renaming base folder

28 files changed, 2675 insertions, 0 deletions

diff --git a/yage/core/CMakeLists.txt b/yage/core/CMakeLists.txt
new file mode 100644
index 00000000..810706ab
--- /dev/null
+++ b/yage/core/CMakeLists.txt
@@ -0,0 +1,15 @@
+set(YAGE_CORE_SOURCES
+  core/imageloader.cpp
+  core/window.cpp
+  core/texturecache.cpp
+  core/glslprogram.cpp
+  core/sprite.cpp
+  core/spritebatch.cpp
+  core/spritesheet.cpp
+  core/resourcemanager.cpp
+  core/sprite.cpp
+  core/inputmanager.cpp
+  core/picopng.cpp
+  core/camera2d.cpp
+  core/iomanager.cpp
+  )
diff --git a/yage/core/camera2d.cpp b/yage/core/camera2d.cpp
new file mode 100644
index 00000000..9eda38ee
--- /dev/null
+++ b/yage/core/camera2d.cpp
@@ -0,0 +1,45 @@
+/* ----------------------------------------------------------------------------
+ * camera2d.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include "camera2d.h"
+
+#include <glad/glad.h>
+
+namespace yage
+{
+
+Camera2D::Camera2D(int screen_width, int screen_height)
+    : position_(0.f, 0.f), camera_matrix_(1.f),
+      ortho_matrix_(
+          glm::ortho(0.f, (float)screen_width, 0.f, (float)screen_height))
+{
+}
+
+void Camera2D::update(GlslProgram &program)
+{
+    if (update_matrix_) {
+        glm::vec3 translate(-position_.x, -position_.y, 0.f);
+        glm::vec3 scale(scale_, scale_, 0.f);
+
+        camera_matrix_ = glm::translate(ortho_matrix_, translate);
+        camera_matrix_ = glm::scale(glm::mat4(1.f), scale) * camera_matrix_;
+
+        update_matrix_ = false;
+    }
+
+    GLint matrix_location = program.getUniformLocation("P");
+    glUniformMatrix4fv(matrix_location, 1, GL_FALSE, &(camera_matrix_[0][0]));
+}
+
+void Camera2D::move(const glm::vec2 &direction)
+{
+    position_ += direction;
+    update_matrix_ = true;
+}
+
+} // namespace yage
diff --git a/yage/core/camera2d.h b/yage/core/camera2d.h
new file mode 100644
index 00000000..a60893ac
--- /dev/null
+++ b/yage/core/camera2d.h
@@ -0,0 +1,38 @@
+/* ----------------------------------------------------------------------------
+ * camera2d.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com>
+ * MIT License, see LICENSE file for more details.
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef YAGE_CAMERA2D_H
+#define YAGE_CAMERA2D_H
+
+#include "glslprogram.h"
+
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
+
+namespace yage
+{
+
+class Camera2D
+{
+private:
+    bool update_matrix_ = true;
+    float scale_ = 1;
+    glm::vec2 position_;
+    glm::mat4 camera_matrix_;
+    glm::mat4 ortho_matrix_;
+
+public:
+    Camera2D(int screen_width = 1280, int screen_height = 720);
+
+    void update(GlslProgram &program);
+    void move(const glm::vec2 &direction);
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/glslprogram.cpp b/yage/core/glslprogram.cpp
new file mode 100644
index 00000000..cff84e40
--- /dev/null
+++ b/yage/core/glslprogram.cpp
@@ -0,0 +1,162 @@
+/* ----------------------------------------------------------------------------
+ * glslprogram.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include "glslprogram.h"
+
+#include <fstream>
+#include <stdexcept>
+#include <vector>
+
+namespace yage
+{
+
+GlslProgram::~GlslProgram()
+{
+    // cleanup all the shaders and the program
+    if (fragment_shader_id_ != 0) {
+        glDeleteShader(fragment_shader_id_);
+    }
+
+    if (vertex_shader_id_ != 0) {
+        glDeleteShader(vertex_shader_id_);
+    }
+
+    if (program_id_ != 0) {
+        glDeleteProgram(program_id_);
+    }
+}
+
+void GlslProgram::compileShader(const GLuint &shader,
+                                const std::string &file_path)
+{
+    // get a string with the input from the shader file
+    std::ifstream file(file_path);
+    if (!file.is_open()) {
+        throw std::runtime_error("Failed to open '" + file_path + "'");
+    }
+
+    std::string content = "";
+    std::string line;
+
+    while (std::getline(file, line)) {
+        content += line + "\n";
+    }
+    file.close();
+
+    // cast source to a c string to get the address of it and input it for
+    // compilation
+    const auto *vertex_source = (const GLchar *)content.c_str();
+    glShaderSource(shader, 1, &vertex_source, nullptr);
+    glCompileShader(shader);
+
+    // check if compilation was successful
+    GLint is_compiled = 0;
+    glGetShaderiv(shader, GL_COMPILE_STATUS, (int *)&is_compiled);
+
+    // if it isn't compiled throw exception to clean up
+    if (is_compiled == GL_FALSE) {
+        GLint max_length = 0;
+        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &max_length);
+
+        std::vector<GLchar> error_log(max_length);
+        glGetShaderInfoLog(shader, max_length, &max_length, &error_log[0]);
+        std::string error_log_str((const char *)&error_log[0]);
+
+        throw std::runtime_error("Couldn't compile " + file_path + " : " +
+                                 error_log_str);
+    }
+}
+
+void GlslProgram::compileShaders(const std::string &vertex_shader_path,
+                                 const std::string &fragment_shader_path)
+{
+    // create the program that will be run on GPU
+    program_id_ = glCreateProgram();
+
+    // create vertex shader
+    vertex_shader_id_ = glCreateShader(GL_VERTEX_SHADER);
+    if (vertex_shader_id_ == 0) {
+        throw std::runtime_error("Vertex shader failed to be created");
+    }
+
+    // create fragment shader
+    fragment_shader_id_ = glCreateShader(GL_FRAGMENT_SHADER);
+    if (fragment_shader_id_ == 0) {
+        throw std::runtime_error("Fragment shader failed to be created");
+    }
+
+    // compile the two shaders
+    compileShader(vertex_shader_id_, vertex_shader_path);
+    compileShader(fragment_shader_id_, fragment_shader_path);
+}
+
+void GlslProgram::linkShaders()
+{
+    // attach the shaders that we want
+    glAttachShader(program_id_, vertex_shader_id_);
+    glAttachShader(program_id_, fragment_shader_id_);
+
+    // link our program
+    glLinkProgram(program_id_);
+
+    GLint is_linked = 0;
+    glGetProgramiv(program_id_, GL_LINK_STATUS, (int *)&is_linked);
+    if (is_linked == GL_FALSE) {
+        GLint max_length = 0;
+        glGetProgramiv(program_id_, GL_INFO_LOG_LENGTH, &max_length);
+
+        std::vector<GLchar> error_log(max_length);
+        glGetProgramInfoLog(program_id_, max_length, &max_length,
+                            &error_log[0]);
+
+        std::string error_log_str((const char *)&error_log[0]);
+
+        throw std::runtime_error("Could not link program : " + error_log_str);
+    }
+
+    // detach shaders after successful link
+    glDetachShader(program_id_, fragment_shader_id_);
+    glDetachShader(program_id_, vertex_shader_id_);
+
+    // we can then delete the shaders once we have the program
+    glDeleteShader(fragment_shader_id_);
+    glDeleteShader(vertex_shader_id_);
+}
+
+void GlslProgram::addAttribute(const std::string &attribute_name)
+{
+    glBindAttribLocation(program_id_, attribute_index_++,
+                         attribute_name.c_str());
+}
+
+GLint GlslProgram::getUniformLocation(const std::string &uniform_name)
+{
+    GLint location = glGetUniformLocation(program_id_, uniform_name.c_str());
+    if ((GLuint)location == GL_INVALID_INDEX) {
+        throw std::runtime_error("'" + uniform_name + "' not found");
+    }
+    return location;
+}
+
+void GlslProgram::use()
+{
+    glUseProgram(program_id_);
+    for (int i = 0; i < attribute_index_; ++i) {
+        glEnableVertexAttribArray(i);
+    }
+}
+
+void GlslProgram::unuse()
+{
+    for (int i = 0; i < attribute_index_; ++i) {
+        glDisableVertexAttribArray(i);
+    }
+    glUseProgram(0);
+}
+
+} // namespace yage
diff --git a/yage/core/glslprogram.h b/yage/core/glslprogram.h
new file mode 100644
index 00000000..545dbe54
--- /dev/null
+++ b/yage/core/glslprogram.h
@@ -0,0 +1,52 @@
+/* ----------------------------------------------------------------------------
+ * glslprogram.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef GLSL_PROGRAM_H
+#define GLSL_PROGRAM_H
+
+#include <glad/glad.h>
+
+#include <string>
+
+namespace yage
+{
+
+class GlslProgram
+{
+private:
+    /// compiled shader program id
+    GLuint program_id_ = 0;
+    GLuint vertex_shader_id_ = 0;
+    GLuint fragment_shader_id_ = 0;
+    int attribute_index_ = 0;
+
+    /// compiles one shader
+    void compileShader(const GLuint &shader, const std::string &file_path);
+
+public:
+    GlslProgram() = default;
+    GlslProgram(const GlslProgram &) = delete;
+    GlslProgram(GlslProgram &&) = delete;
+    ~GlslProgram();
+
+    GlslProgram &operator=(const GlslProgram &) = delete;
+    GlslProgram &operator=(GlslProgram &&) = delete;
+
+    /// compiles vertex and fragment shader
+    void compileShaders(const std::string &vertex_shader_path,
+                        const std::string &fragment_shader_path);
+    void linkShaders();
+    void addAttribute(const std::string &attribute_name);
+    GLint getUniformLocation(const std::string &uniform_name);
+    void use();
+    void unuse();
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/imageloader.cpp b/yage/core/imageloader.cpp
new file mode 100644
index 00000000..e1d54dc1
--- /dev/null
+++ b/yage/core/imageloader.cpp
@@ -0,0 +1,64 @@
+/* ----------------------------------------------------------------------------
+ * imageloader.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include "imageloader.h"
+
+#ifndef UNIT_TESTS
+#include <glad/glad.h>
+#endif
+
+#include <yage/base/iomanager.h>
+#include <yage/base/picopng.h>
+
+#include <iostream>
+#include <stdexcept>
+
+namespace yage
+{
+
+Texture ImageLoader::loadPng(const std::string &file_path)
+{
+    std::vector<unsigned char> in;
+    std::vector<unsigned char> out;
+    unsigned long width, height;
+
+    if (!IoManager::readFileToBuffer(file_path, in)) {
+        throw std::runtime_error("Failed to load '" + file_path +
+                                 "' to buffer");
+    }
+
+    int error_code = decodePNG(out, width, height, &in[0], in.size());
+    if (error_code != 0) {
+        throw std::runtime_error("Failed to load '" + file_path +
+                                 "' to png with error code" +
+                                 std::to_string(error_code));
+    }
+
+    Texture texture(0, static_cast<int>(width), static_cast<int>(height));
+    std::cout << "Geometry: " << texture.width << "x" << texture.height << "\n";
+
+    glGenTextures(1, &texture.id);
+
+    glBindTexture(GL_TEXTURE_2D, texture.id);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
+                 GL_UNSIGNED_BYTE, &out[0]);
+
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
+                    GL_LINEAR_MIPMAP_LINEAR);
+
+    glGenerateMipmap(GL_TEXTURE_2D);
+
+    glBindTexture(GL_TEXTURE_2D, 0);
+
+    return texture;
+}
+
+} // namespace yage
diff --git a/yage/core/imageloader.h b/yage/core/imageloader.h
new file mode 100644
index 00000000..8d5c5cd1
--- /dev/null
+++ b/yage/core/imageloader.h
@@ -0,0 +1,27 @@
+/* ----------------------------------------------------------------------------
+ * imageloader.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef IMAGE_LOADER_H
+#define IMAGE_LOADER_H
+
+#include "texture.h"
+
+#include <string>
+
+namespace yage
+{
+
+class ImageLoader
+{
+public:
+    static Texture loadPng(const std::string &file_path);
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/inputmanager.cpp b/yage/core/inputmanager.cpp
new file mode 100644
index 00000000..15ff374b
--- /dev/null
+++ b/yage/core/inputmanager.cpp
@@ -0,0 +1,33 @@
+/* ----------------------------------------------------------------------------
+ * inputmanager.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/inputmanager.h>
+
+namespace yage
+{
+
+void InputManager::keyPressed(unsigned key)
+{
+    key_map_[key] = true;
+}
+
+void InputManager::keyReleased(unsigned key)
+{
+    key_map_[key] = false;
+}
+
+bool InputManager::isKeyPressed(unsigned key) const
+{
+    auto key_index = key_map_.find(key);
+    if (key_index != key_map_.end()) {
+        return key_index->second;
+    }
+    return false;
+}
+
+} // namespace yage
diff --git a/yage/core/inputmanager.h b/yage/core/inputmanager.h
new file mode 100644
index 00000000..84728fff
--- /dev/null
+++ b/yage/core/inputmanager.h
@@ -0,0 +1,28 @@
+/* ----------------------------------------------------------------------------
+ * inputmanager.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef INPUT_MANAGER_H
+#define INPUT_MANAGER_H
+
+#include <unordered_map>
+
+namespace yage
+{
+
+class InputManager
+{
+private:
+    std::unordered_map<unsigned, bool> key_map_;
+
+public:
+    void keyPressed(unsigned key);
+    void keyReleased(unsigned key);
+    bool isKeyPressed(unsigned key) const;
+};
+} // namespace yage
+#endif
diff --git a/yage/core/iomanager.cpp b/yage/core/iomanager.cpp
new file mode 100644
index 00000000..d5b950d6
--- /dev/null
+++ b/yage/core/iomanager.cpp
@@ -0,0 +1,42 @@
+/* ----------------------------------------------------------------------------
+ * iomanager.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/iomanager.h>
+
+#include <fstream>
+#include <stdexcept>
+
+namespace yage
+{
+
+bool IoManager::readFileToBuffer(const std::string &file_path,
+                                 std::vector<unsigned char> &buffer)
+{
+    std::ifstream file(file_path, std::ios::binary);
+    if (!file.is_open()) {
+        throw std::runtime_error("Could not open '" + file_path + "'");
+    }
+
+    // seek to the end
+    file.seekg(0, std::ios::end);
+
+    // get the file size
+    int file_size = file.tellg();
+    file.seekg(0, std::ios::beg);
+
+    // reduce file size by header bytes
+    file_size -= file.tellg();
+
+    buffer.resize(file_size);
+    file.read((char *)&buffer[0], file_size);
+    file.close();
+
+    return true;
+}
+
+} // namespace yage
diff --git a/yage/core/iomanager.h b/yage/core/iomanager.h
new file mode 100644
index 00000000..95abd652
--- /dev/null
+++ b/yage/core/iomanager.h
@@ -0,0 +1,27 @@
+/* ----------------------------------------------------------------------------
+ * iomanager.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef IO_MANAGER_H
+#define IO_MANAGER_H
+
+#include <string>
+#include <vector>
+
+namespace yage
+{
+
+class IoManager
+{
+public:
+    static bool readFileToBuffer(const std::string &file_path,
+                                 std::vector<unsigned char> &buffer);
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/logger.h b/yage/core/logger.h
new file mode 100644
index 00000000..90a958d5
--- /dev/null
+++ b/yage/core/logger.h
@@ -0,0 +1,6 @@
+#ifndef YAGE_LOGGER_H
+#define YAGE_LOGGER_H
+
+
+
+#endif
diff --git a/yage/core/picopng.cpp b/yage/core/picopng.cpp
new file mode 100644
index 00000000..dcc4b367
--- /dev/null
+++ b/yage/core/picopng.cpp
@@ -0,0 +1,1118 @@
+#include <cstdlib>
+#include <vector>
+
+namespace yage
+{
+
+/*
+  decodePNG: The picoPNG function, decodes a PNG file buffer in memory, into a
+  raw pixel buffer.
+  out_image: output parameter, this will contain the raw pixels after decoding.
+  By default the output is 32-bit RGBA color.
+  The std::vector is automatically resized to the correct size.
+  image_width: output_parameter, this will contain the width of the image in
+  pixels.
+  image_height: output_parameter, this will contain the height of the image in
+  pixels.
+  in_png: pointer to the buffer of the PNG file in memory. To get it from a file
+  on
+  disk, load it and store it in a memory buffer yourself first.
+  in_size: size of the input PNG file in bytes.
+  convert_to_rgba32: optional parameter, true by default.
+  Set to true to get the output in RGBA 32-bit (8 bit per channel) color format
+  no matter what color type the original PNG image had. This gives predictable,
+  useable data from any random input PNG.
+  Set to false to do no color conversion at all. The result then has the same
+  data
+  type as the PNG image, which can range from 1 bit to 64 bits per pixel.
+  Information about the color type or palette colors are not provided. You need
+  to know this information yourself to be able to use the data so this only
+  works for trusted PNG files. Use LodePNG instead of picoPNG if you need this
+  information.
+  return: 0 if success, not 0 if some error occured.
+*/
+int decodePNG(std::vector<unsigned char> &out_image, unsigned long &image_width,
+              unsigned long &image_height, const unsigned char *in_png,
+              size_t in_size, bool convert_to_rgba32)
+{
+    // picoPNG version 20101224
+    // Copyright (c) 2005-2010 Lode Vandevenne
+    //
+    // This software is provided 'as-is', without any express or implied
+    // warranty. In no event will the authors be held liable for any damages
+    // arising from the use of this software.
+    //
+    // Permission is granted to anyone to use this software for any purpose,
+    // including commercial applications, and to alter it and redistribute it
+    // freely, subject to the following restrictions:
+    //
+    //     1. The origin of this software must not be misrepresented; you must
+    //     not
+    //     claim that you wrote the original software. If you use this software
+    //     in a product, an acknowledgment in the product documentation would be
+    //     appreciated but is not required.
+    //     2. Altered source versions must be plainly marked as such, and must
+    //     not be
+    //     misrepresented as being the original software.
+    //     3. This notice may not be removed or altered from any source
+    //     distribution.
+
+    // picoPNG is a PNG decoder in one C++ function of around 500 lines. Use
+    // picoPNG for
+    // programs that need only 1 .cpp file. Since it's a single function, it's
+    // very limited,
+    // it can convert a PNG to raw pixel data either converted to 32-bit RGBA
+    // color or
+    // with no color conversion at all. For anything more complex, another tiny
+    // library
+    // is available: LodePNG (lodepng.c(pp)), which is a single source and
+    // header file.
+    // Apologies for the compact code style, it's to make this tiny.
+
+    static const unsigned long LENBASE[29] = {
+        3,  4,  5,  6,  7,  8,  9,  10, 11,  13,  15,  17,  19,  23, 27,
+        31, 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258};
+    static const unsigned long LENEXTRA[29] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
+                                               1, 1, 2, 2, 2, 2, 3, 3, 3, 3,
+                                               4, 4, 4, 4, 5, 5, 5, 5, 0};
+    static const unsigned long DISTBASE[30] = {
+        1,    2,    3,    4,    5,    7,    9,    13,    17,    25,
+        33,   49,   65,   97,   129,  193,  257,  385,   513,   769,
+        1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577};
+    static const unsigned long DISTEXTRA[30] = {
+        0, 0, 0, 0, 1, 1, 2, 2,  3,  3,  4,  4,  5,  5,  6,
+        6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13};
+    static const unsigned long CLCL[19] = {
+        16, 17, 18, 0, 8,  7, 9,  6, 10, 5,
+        11, 4,  12, 3, 13, 2, 14, 1, 15}; // code length code lengths
+    struct Zlib // nested functions for zlib decompression
+    {
+        static unsigned long readBitFromStream(size_t &bitp,
+                                               const unsigned char *bits)
+        {
+            unsigned long result = (bits[bitp >> 3] >> (bitp & 0x7)) & 1;
+            bitp++;
+            return result;
+        }
+        static unsigned long readBitsFromStream(size_t &bitp,
+                                                const unsigned char *bits,
+                                                size_t nbits)
+        {
+            unsigned long result = 0;
+            for (size_t i = 0; i < nbits; i++) {
+                result += (readBitFromStream(bitp, bits)) << i;
+            }
+            return result;
+        }
+        struct HuffmanTree {
+            int makeFromLengths(const std::vector<unsigned long> &bitlen,
+                                unsigned long maxbitlen)
+            { // make tree given the lengths
+                unsigned long numcodes = (unsigned long)(bitlen.size()),
+                              treepos = 0, nodefilled = 0;
+                std::vector<unsigned long> tree1d(numcodes),
+                    blcount(maxbitlen + 1, 0), nextcode(maxbitlen + 1, 0);
+                for (unsigned long bits = 0; bits < numcodes; bits++) {
+                    blcount[bitlen[bits]]++; // count number of instances of
+                }
+                // each code length
+                for (unsigned long bits = 1; bits <= maxbitlen; bits++) {
+                    nextcode[bits] = (nextcode[bits - 1] + blcount[bits - 1])
+                                     << 1;
+                }
+                for (unsigned long n = 0; n < numcodes; n++) {
+                    if (bitlen[n] != 0) {
+                        tree1d[n] =
+                            nextcode[bitlen[n]]++; // generate all the codes
+                    }
+                }
+                tree2d.clear();
+                tree2d.resize(numcodes * 2, 32767); // 32767 here means the
+                                                    // tree2d isn't filled
+                                                    // there yet
+                for (unsigned long n = 0; n < numcodes; n++) { // the codes
+                    for (unsigned long i = 0; i < bitlen[n];
+                         i++) // the bits for this code
+                    {
+                        unsigned long bit =
+                            (tree1d[n] >> (bitlen[n] - i - 1)) & 1;
+                        if (treepos > numcodes - 2) {
+                            return 55;
+                        }
+                        if (tree2d[2 * treepos + bit] ==
+                            32767) // not yet filled in
+                        {
+                            if (i + 1 == bitlen[n]) {
+                                tree2d[2 * treepos + bit] = n;
+                                treepos = 0;
+                            } // last bit
+                            else {
+                                tree2d[2 * treepos + bit] =
+                                    ++nodefilled + numcodes;
+                                treepos = nodefilled;
+                            } // addresses are encoded as values > numcodes
+                        } else {
+                            treepos = tree2d[2 * treepos + bit] -
+                                      numcodes; // subtract numcodes from
+                        }
+                        // address to get address value
+                    }
+                }
+                return 0;
+            }
+            int decode(bool &decoded, unsigned long &result, size_t &treepos,
+                       unsigned long bit) const
+            { // Decodes a symbol from the tree
+                unsigned long numcodes = (unsigned long)tree2d.size() / 2;
+                if (treepos >= numcodes) {
+                    return 11; // error: you appeared outside the codetree
+                }
+                result = tree2d[2 * treepos + bit];
+                decoded = (result < numcodes);
+                treepos = decoded ? 0 : result - numcodes;
+                return 0;
+            }
+            std::vector<unsigned long> tree2d; // 2D representation of a
+                                               // huffman tree: The one
+                                               // dimension is "0" or "1", the
+                                               // other contains all nodes and
+                                               // leaves of the tree.
+        };
+        struct Inflator {
+            int error;
+            void inflate(std::vector<unsigned char> &out,
+                         const std::vector<unsigned char> &in, size_t inpos = 0)
+            {
+                size_t bp = 0, pos = 0; // bit pointer and byte pointer
+                error = 0;
+                unsigned long BFINAL = 0;
+                while (!BFINAL && !error) {
+                    if (bp >> 3 >= in.size()) {
+                        error = 52;
+                        return;
+                    } // error, bit pointer will jump past memory
+                    BFINAL = readBitFromStream(bp, &in[inpos]);
+                    unsigned long BTYPE = readBitFromStream(bp, &in[inpos]);
+                    BTYPE += 2 * readBitFromStream(bp, &in[inpos]);
+                    if (BTYPE == 3) {
+                        error = 20;
+                        return;
+                    } // error: invalid BTYPE
+                    else if (BTYPE == 0) {
+                        inflateNoCompression(out, &in[inpos], bp, pos,
+                                             in.size());
+                    } else {
+                        inflateHuffmanBlock(out, &in[inpos], bp, pos, in.size(),
+                                            BTYPE);
+                    }
+                }
+                if (!error) {
+                    out.resize(pos); // Only now we know the true size of out,
+                }
+                // resize it to that
+            }
+            void generateFixedTrees(HuffmanTree &tree,
+                                    HuffmanTree &treeD) // get the tree of a
+                                                        // deflated block with
+                                                        // fixed tree
+            {
+                std::vector<unsigned long> bitlen(288, 8), bitlenD(32, 5);
+                ;
+                for (size_t i = 144; i <= 255; i++) {
+                    bitlen[i] = 9;
+                }
+                for (size_t i = 256; i <= 279; i++) {
+                    bitlen[i] = 7;
+                }
+                tree.makeFromLengths(bitlen, 15);
+                treeD.makeFromLengths(bitlenD, 15);
+            }
+            HuffmanTree codetree, codetreeD,
+                codelengthcodetree; // the code tree for Huffman codes, dist
+                                    // codes, and code length codes
+            unsigned long huffmanDecodeSymbol(const unsigned char *in,
+                                              size_t &bp,
+                                              const HuffmanTree &codetree,
+                                              size_t inlength)
+            { // decode a single symbol from given list of
+                // bits with given code tree. return value
+                // is the symbol
+                bool decoded;
+                unsigned long ct;
+                for (size_t treepos = 0;;) {
+                    if ((bp & 0x07) == 0 && (bp >> 3) > inlength) {
+                        error = 10;
+                        return 0;
+                    } // error: end reached without endcode
+                    error = codetree.decode(decoded, ct, treepos,
+                                            readBitFromStream(bp, in));
+                    if (error) {
+                        return 0; // stop, an error happened
+                    }
+                    if (decoded) {
+                        return ct;
+                    }
+                }
+            }
+            void getTreeInflateDynamic(HuffmanTree &tree, HuffmanTree &treeD,
+                                       const unsigned char *in, size_t &bp,
+                                       size_t inlength)
+            { // get the tree of a deflated block with
+                // dynamic tree, the tree itself is also
+                // Huffman compressed with a known tree
+                std::vector<unsigned long> bitlen(288, 0), bitlenD(32, 0);
+                if (bp >> 3 >= inlength - 2) {
+                    error = 49;
+                    return;
+                } // the bit pointer is or will go past the memory
+                size_t HLIT = readBitsFromStream(bp, in, 5) +
+                              257; // number of literal/length codes + 257
+                size_t HDIST = readBitsFromStream(bp, in, 5) +
+                               1; // number of dist codes + 1
+                size_t HCLEN = readBitsFromStream(bp, in, 4) +
+                               4; // number of code length codes + 4
+                std::vector<unsigned long> codelengthcode(
+                    19); // lengths of tree to decode the lengths of the
+                         // dynamic tree
+                for (size_t i = 0; i < 19; i++) {
+                    codelengthcode[CLCL[i]] =
+                        (i < HCLEN) ? readBitsFromStream(bp, in, 3) : 0;
+                }
+                error = codelengthcodetree.makeFromLengths(codelengthcode, 7);
+                if (error) {
+                    return;
+                }
+                size_t i = 0, replength;
+                while (i < HLIT + HDIST) {
+                    unsigned long code = huffmanDecodeSymbol(
+                        in, bp, codelengthcodetree, inlength);
+                    if (error) {
+                        return;
+                    }
+                    if (code <= 15) {
+                        if (i < HLIT) {
+                            bitlen[i++] = code;
+                        } else {
+                            bitlenD[i++ - HLIT] = code;
+                        }
+                    }                    // a length code
+                    else if (code == 16) // repeat previous
+                    {
+                        if (bp >> 3 >= inlength) {
+                            error = 50;
+                            return;
+                        } // error, bit pointer jumps past memory
+                        replength = 3 + readBitsFromStream(bp, in, 2);
+                        unsigned long value; // set value to the previous code
+                        if ((i - 1) < HLIT) {
+                            value = bitlen[i - 1];
+                        } else {
+                            value = bitlenD[i - HLIT - 1];
+                        }
+                        for (size_t n = 0; n < replength;
+                             n++) // repeat this value in the next lengths
+                        {
+                            if (i >= HLIT + HDIST) {
+                                error = 13;
+                                return;
+                            } // error: i is larger than the amount of codes
+                            if (i < HLIT) {
+                                bitlen[i++] = value;
+                            } else {
+                                bitlenD[i++ - HLIT] = value;
+                            }
+                        }
+                    } else if (code == 17) // repeat "0" 3-10 times
+                    {
+                        if (bp >> 3 >= inlength) {
+                            error = 50;
+                            return;
+                        } // error, bit pointer jumps past memory
+                        replength = 3 + readBitsFromStream(bp, in, 3);
+                        for (size_t n = 0; n < replength;
+                             n++) // repeat this value in the next lengths
+                        {
+                            if (i >= HLIT + HDIST) {
+                                error = 14;
+                                return;
+                            } // error: i is larger than the amount of codes
+                            if (i < HLIT) {
+                                bitlen[i++] = 0;
+                            } else {
+                                bitlenD[i++ - HLIT] = 0;
+                            }
+                        }
+                    } else if (code == 18) // repeat "0" 11-138 times
+                    {
+                        if (bp >> 3 >= inlength) {
+                            error = 50;
+                            return;
+                        } // error, bit pointer jumps past memory
+                        replength = 11 + readBitsFromStream(bp, in, 7);
+                        for (size_t n = 0; n < replength;
+                             n++) // repeat this value in the next lengths
+                        {
+                            if (i >= HLIT + HDIST) {
+                                error = 15;
+                                return;
+                            } // error: i is larger than the amount of codes
+                            if (i < HLIT) {
+                                bitlen[i++] = 0;
+                            } else {
+                                bitlenD[i++ - HLIT] = 0;
+                            }
+                        }
+                    } else {
+                        error = 16;
+                        return;
+                    } // error: somehow an unexisting code appeared. This can
+                    // never happen.
+                }
+                if (bitlen[256] == 0) {
+                    error = 64;
+                    return;
+                } // the length of the end code 256 must be larger than 0
+                error = tree.makeFromLengths(bitlen, 15);
+                if (error) {
+                    return; // now we've finally got HLIT and HDIST, so
+                }
+                // generate the code trees, and the function is
+                // done
+                error = treeD.makeFromLengths(bitlenD, 15);
+                if (error) {
+                    return;
+                }
+            }
+            void inflateHuffmanBlock(std::vector<unsigned char> &out,
+                                     const unsigned char *in, size_t &bp,
+                                     size_t &pos, size_t inlength,
+                                     unsigned long btype)
+            {
+                if (btype == 1) {
+                    generateFixedTrees(codetree, codetreeD);
+                } else if (btype == 2) {
+                    getTreeInflateDynamic(codetree, codetreeD, in, bp,
+                                          inlength);
+                    if (error) {
+                        return;
+                    }
+                }
+                for (;;) {
+                    unsigned long code =
+                        huffmanDecodeSymbol(in, bp, codetree, inlength);
+                    if (error) {
+                        return;
+                    }
+                    if (code == 256) {
+                        return;             // end code
+                    } else if (code <= 255) // literal symbol
+                    {
+                        if (pos >= out.size()) {
+                            out.resize((pos + 1) * 2); // reserve more room
+                        }
+                        out[pos++] = (unsigned char)(code);
+                    } else if (code >= 257 && code <= 285) // length code
+                    {
+                        size_t length = LENBASE[code - 257],
+                               numextrabits = LENEXTRA[code - 257];
+                        if ((bp >> 3) >= inlength) {
+                            error = 51;
+                            return;
+                        } // error, bit pointer will jump past memory
+                        length += readBitsFromStream(bp, in, numextrabits);
+                        unsigned long codeD =
+                            huffmanDecodeSymbol(in, bp, codetreeD, inlength);
+                        if (error) {
+                            return;
+                        }
+                        if (codeD > 29) {
+                            error = 18;
+                            return;
+                        } // error: invalid dist code (30-31 are never used)
+                        unsigned long dist = DISTBASE[codeD],
+                                      numextrabitsD = DISTEXTRA[codeD];
+                        if ((bp >> 3) >= inlength) {
+                            error = 51;
+                            return;
+                        } // error, bit pointer will jump past memory
+                        dist += readBitsFromStream(bp, in, numextrabitsD);
+                        size_t start = pos, back = start - dist; // backwards
+                        if (pos + length >= out.size()) {
+                            out.resize((pos + length) * 2); // reserve more
+                        }
+                        // room
+                        for (size_t i = 0; i < length; i++) {
+                            out[pos++] = out[back++];
+                            if (back >= start) {
+                                back = start - dist;
+                            }
+                        }
+                    }
+                }
+            }
+            void inflateNoCompression(std::vector<unsigned char> &out,
+                                      const unsigned char *in, size_t &bp,
+                                      size_t &pos, size_t inlength)
+            {
+                while ((bp & 0x7) != 0) {
+                    bp++; // go to first boundary of byte
+                }
+                size_t p = bp / 8;
+                if (p >= inlength - 4) {
+                    error = 52;
+                    return;
+                } // error, bit pointer will jump past memory
+                unsigned long LEN = in[p] + 256 * in[p + 1],
+                              NLEN = in[p + 2] + 256 * in[p + 3];
+                p += 4;
+                if (LEN + NLEN != 65535) {
+                    error = 21;
+                    return;
+                } // error: NLEN is not one's complement of LEN
+                if (pos + LEN >= out.size()) {
+                    out.resize(pos + LEN);
+                }
+                if (p + LEN > inlength) {
+                    error = 23;
+                    return;
+                } // error: reading outside of in buffer
+                for (unsigned long n = 0; n < LEN; n++) {
+                    out[pos++] = in[p++]; // read LEN bytes of literal data
+                }
+                bp = p * 8;
+            }
+        };
+        int
+        decompress(std::vector<unsigned char> &out,
+                   const std::vector<unsigned char> &in) // returns error value
+        {
+            Inflator inflator;
+            if (in.size() < 2) {
+                return 53;
+            } // error, size of zlib data too small
+            if ((in[0] * 256 + in[1]) % 31 != 0) {
+                return 24;
+            } // error: 256 * in[0] + in[1] must be a multiple of 31, the
+            // FCHECK value is supposed to be made that way
+            unsigned long CM = in[0] & 15, CINFO = (in[0] >> 4) & 15,
+                          FDICT = (in[1] >> 5) & 1;
+            if (CM != 8 || CINFO > 7) {
+                return 25;
+            } // error: only compression method 8: inflate with sliding window
+            // of 32k is supported by the PNG spec
+            if (FDICT != 0) {
+                return 26;
+            } // error: the specification of PNG says about the zlib stream:
+            // "The additional flags shall not specify a preset dictionary."
+            inflator.inflate(out, in, 2);
+            return inflator
+                .error; // note: adler32 checksum was skipped and ignored
+        }
+    };
+    struct PNG // nested functions for PNG decoding
+    {
+        struct Info {
+            unsigned long width, height, colorType, bitDepth, compressionMethod,
+                filterMethod, interlaceMethod, key_r, key_g, key_b;
+            bool key_defined; // is a transparent color key given?
+            std::vector<unsigned char> palette;
+        } info;
+        int error;
+        void decode(std::vector<unsigned char> &out, const unsigned char *in,
+                    size_t size, bool convert_to_rgba32)
+        {
+            error = 0;
+            if (size == 0 || in == nullptr) {
+                error = 48;
+                return;
+            } // the given data is empty
+            readPngHeader(&in[0], size);
+            if (error) {
+                return;
+            }
+            size_t pos = 33; // first byte of the first chunk after the header
+            std::vector<unsigned char> idat; // the data from idat chunks
+            bool IEND = false, known_type = true;
+            info.key_defined = false;
+            while (!IEND) // loop through the chunks, ignoring unknown chunks
+                          // and stopping at IEND chunk. IDAT data is put at
+                          // the start of the in buffer
+            {
+                if (pos + 8 >= size) {
+                    error = 30;
+                    return;
+                } // error: size of the in buffer too small to contain next
+                // chunk
+                size_t chunkLength = read32bitInt(&in[pos]);
+                pos += 4;
+                if (chunkLength > 2147483647) {
+                    error = 63;
+                    return;
+                }
+                if (pos + chunkLength >= size) {
+                    error = 35;
+                    return;
+                } // error: size of the in buffer too small to contain next
+                // chunk
+                if (in[pos + 0] == 'I' && in[pos + 1] == 'D' &&
+                    in[pos + 2] == 'A' &&
+                    in[pos + 3] ==
+                        'T') // IDAT chunk, containing compressed image data
+                {
+                    idat.insert(idat.end(), &in[pos + 4],
+                                &in[pos + 4 + chunkLength]);
+                    pos += (4 + chunkLength);
+                } else if (in[pos + 0] == 'I' && in[pos + 1] == 'E' &&
+                           in[pos + 2] == 'N' && in[pos + 3] == 'D') {
+                    pos += 4;
+                    IEND = true;
+                } else if (in[pos + 0] == 'P' && in[pos + 1] == 'L' &&
+                           in[pos + 2] == 'T' &&
+                           in[pos + 3] == 'E') // palette chunk (PLTE)
+                {
+                    pos += 4; // go after the 4 letters
+                    info.palette.resize(4 * (chunkLength / 3));
+                    if (info.palette.size() > (4 * 256)) {
+                        error = 38;
+                        return;
+                    } // error: palette too big
+                    for (size_t i = 0; i < info.palette.size(); i += 4) {
+                        for (size_t j = 0; j < 3; j++) {
+                            info.palette[i + j] = in[pos++]; // RGB
+                        }
+                        info.palette[i + 3] = 255; // alpha
+                    }
+                } else if (in[pos + 0] == 't' && in[pos + 1] == 'R' &&
+                           in[pos + 2] == 'N' &&
+                           in[pos + 3] ==
+                               'S') // palette transparency chunk (tRNS)
+                {
+                    pos += 4; // go after the 4 letters
+                    if (info.colorType == 3) {
+                        if (4 * chunkLength > info.palette.size()) {
+                            error = 39;
+                            return;
+                        } // error: more alpha values given than there are
+                        // palette entries
+                        for (size_t i = 0; i < chunkLength; i++) {
+                            info.palette[4 * i + 3] = in[pos++];
+                        }
+                    } else if (info.colorType == 0) {
+                        if (chunkLength != 2) {
+                            error = 40;
+                            return;
+                        } // error: this chunk must be 2 bytes for greyscale
+                        // image
+                        info.key_defined = true;
+                        info.key_r = info.key_g = info.key_b =
+                            256 * in[pos] + in[pos + 1];
+                        pos += 2;
+                    } else if (info.colorType == 2) {
+                        if (chunkLength != 6) {
+                            error = 41;
+                            return;
+                        } // error: this chunk must be 6 bytes for RGB image
+                        info.key_defined = true;
+                        info.key_r = 256 * in[pos] + in[pos + 1];
+                        pos += 2;
+                        info.key_g = 256 * in[pos] + in[pos + 1];
+                        pos += 2;
+                        info.key_b = 256 * in[pos] + in[pos + 1];
+                        pos += 2;
+                    } else {
+                        error = 42;
+                        return;
+                    }  // error: tRNS chunk not allowed for other color models
+                } else // it's not an implemented chunk type, so ignore it:
+                       // skip over the data
+                {
+                    if (!(in[pos + 0] & 32)) {
+                        error = 69;
+                        return;
+                    } // error: unknown critical chunk (5th bit of first byte
+                    // of chunk type is 0)
+                    pos += (chunkLength + 4); // skip 4 letters and
+                                              // uninterpreted data of
+                                              // unimplemented chunk
+                    known_type = false;
+                }
+                pos += 4; // step over CRC (which is ignored)
+            }
+            unsigned long bpp = getBpp(info);
+            std::vector<unsigned char> scanlines(
+                ((info.width * (info.height * bpp + 7)) / 8) +
+                info.height); // now the out buffer will be filled
+            Zlib zlib;        // decompress with the Zlib decompressor
+            error = zlib.decompress(scanlines, idat);
+            if (error) {
+                return; // stop if the zlib decompressor returned an error
+            }
+            size_t bytewidth = (bpp + 7) / 8,
+                   outlength = (info.height * info.width * bpp + 7) / 8;
+            out.resize(outlength); // time to fill the out buffer
+            unsigned char *out_ =
+                outlength ? &out[0] : nullptr; // use a regular pointer to the
+                                               // std::vector for faster code if
+                                               // compiled without optimization
+            if (info.interlaceMethod == 0)     // no interlace, just filter
+            {
+                size_t linestart = 0,
+                       linelength = (info.width * bpp + 7) /
+                                    8; // length in bytes of a scanline,
+                                       // excluding the filtertype byte
+                if (bpp >= 8) {        // byte per byte
+                    for (unsigned long y = 0; y < info.height; y++) {
+                        unsigned long filterType = scanlines[linestart];
+                        const unsigned char *prevline =
+                            (y == 0) ? nullptr
+                                     : &out_[(y - 1) * info.width * bytewidth];
+                        unFilterScanline(&out_[linestart - y],
+                                         &scanlines[linestart + 1], prevline,
+                                         bytewidth, filterType, linelength);
+                        if (error) {
+                            return;
+                        }
+                        linestart +=
+                            (1 + linelength); // go to start of next scanline
+                    }
+                } else // less than 8 bits per pixel, so fill it up bit per bit
+                {
+                    std::vector<unsigned char> templine(
+                        (info.width * bpp + 7) >> 3); // only used if bpp < 8
+                    for (size_t y = 0, obp = 0; y < info.height; y++) {
+                        unsigned long filterType = scanlines[linestart];
+                        const unsigned char *prevline =
+                            (y == 0) ? nullptr
+                                     : &out_[(y - 1) * info.width * bytewidth];
+                        unFilterScanline(&templine[0],
+                                         &scanlines[linestart + 1], prevline,
+                                         bytewidth, filterType, linelength);
+                        if (error) {
+                            return;
+                        }
+                        for (size_t bp = 0; bp < info.width * bpp;) {
+                            setBitOfReversedStream(
+                                obp, out_,
+                                readBitFromReversedStream(bp, &templine[0]));
+                        }
+                        linestart +=
+                            (1 + linelength); // go to start of next scanline
+                    }
+                }
+            } else // interlaceMethod is 1 (Adam7)
+            {
+                size_t passw[7] = {(info.width + 7) / 8, (info.width + 3) / 8,
+                                   (info.width + 3) / 4, (info.width + 1) / 4,
+                                   (info.width + 1) / 2, (info.width + 0) / 2,
+                                   (info.width + 0) / 1};
+                size_t passh[7] = {(info.height + 7) / 8, (info.height + 7) / 8,
+                                   (info.height + 3) / 8, (info.height + 3) / 4,
+                                   (info.height + 1) / 4, (info.height + 1) / 2,
+                                   (info.height + 0) / 2};
+                size_t passstart[7] = {0};
+                size_t pattern[28] = {0, 4, 0, 2, 0, 1, 0, 0, 0, 4,
+                                      0, 2, 0, 1, 8, 8, 4, 4, 2, 2,
+                                      1, 8, 8, 8, 4, 4, 2, 2}; // values for the
+                                                               // adam7 passes
+                for (int i = 0; i < 6; i++) {
+                    passstart[i + 1] = passstart[i] +
+                                       passh[i] * ((passw[i] ? 1 : 0) +
+                                                   (passw[i] * bpp + 7) / 8);
+                }
+                std::vector<unsigned char> scanlineo((info.width * bpp + 7) /
+                                                     8),
+                    scanlinen((info.width * bpp + 7) /
+                              8); //"old" and "new" scanline
+                for (int i = 0; i < 7; i++) {
+                    adam7Pass(&out_[0], &scanlinen[0], &scanlineo[0],
+                              &scanlines[passstart[i]], info.width, pattern[i],
+                              pattern[i + 7], pattern[i + 14], pattern[i + 21],
+                              passw[i], passh[i], bpp);
+                }
+            }
+            if (convert_to_rgba32 && (info.colorType != 6 ||
+                                      info.bitDepth != 8)) // conversion needed
+            {
+                std::vector<unsigned char> data = out;
+                error = convert(out, &data[0], info, info.width, info.height);
+            }
+        }
+        void readPngHeader(const unsigned char *in,
+                           size_t inlength) // read the information from the
+                                            // header and store it in the Info
+        {
+            if (inlength < 29) {
+                error = 27;
+                return;
+            } // error: the data length is smaller than the length of the
+            // header
+            if (in[0] != 137 || in[1] != 80 || in[2] != 78 || in[3] != 71 ||
+                in[4] != 13 || in[5] != 10 || in[6] != 26 || in[7] != 10) {
+                error = 28;
+                return;
+            } // no PNG signature
+            if (in[12] != 'I' || in[13] != 'H' || in[14] != 'D' ||
+                in[15] != 'R') {
+                error = 29;
+                return;
+            } // error: it doesn't start with a IHDR chunk!
+            info.width = read32bitInt(&in[16]);
+            info.height = read32bitInt(&in[20]);
+            info.bitDepth = in[24];
+            info.colorType = in[25];
+            info.compressionMethod = in[26];
+            if (in[26] != 0) {
+                error = 32;
+                return;
+            } // error: only compression method 0 is allowed in the
+            // specification
+            info.filterMethod = in[27];
+            if (in[27] != 0) {
+                error = 33;
+                return;
+            } // error: only filter method 0 is allowed in the specification
+            info.interlaceMethod = in[28];
+            if (in[28] > 1) {
+                error = 34;
+                return;
+            } // error: only interlace methods 0 and 1 exist in the
+            // specification
+            error = checkColorValidity(info.colorType, info.bitDepth);
+        }
+        void unFilterScanline(unsigned char *recon,
+                              const unsigned char *scanline,
+                              const unsigned char *precon, size_t bytewidth,
+                              unsigned long filterType, size_t length)
+        {
+            switch (filterType) {
+            case 0:
+                for (size_t i = 0; i < length; i++) {
+                    recon[i] = scanline[i];
+                }
+                break;
+            case 1:
+                for (size_t i = 0; i < bytewidth; i++) {
+                    recon[i] = scanline[i];
+                }
+                for (size_t i = bytewidth; i < length; i++) {
+                    recon[i] = scanline[i] + recon[i - bytewidth];
+                }
+                break;
+            case 2:
+                if (precon) {
+                    for (size_t i = 0; i < length; i++) {
+                        recon[i] = scanline[i] + precon[i];
+                    }
+                } else {
+                    for (size_t i = 0; i < length; i++) {
+                        recon[i] = scanline[i];
+                    }
+                }
+                break;
+            case 3:
+                if (precon) {
+                    for (size_t i = 0; i < bytewidth; i++) {
+                        recon[i] = scanline[i] + precon[i] / 2;
+                    }
+                    for (size_t i = bytewidth; i < length; i++) {
+                        recon[i] = scanline[i] +
+                                   ((recon[i - bytewidth] + precon[i]) / 2);
+                    }
+                } else {
+                    for (size_t i = 0; i < bytewidth; i++) {
+                        recon[i] = scanline[i];
+                    }
+                    for (size_t i = bytewidth; i < length; i++) {
+                        recon[i] = scanline[i] + recon[i - bytewidth] / 2;
+                    }
+                }
+                break;
+            case 4:
+                if (precon) {
+                    for (size_t i = 0; i < bytewidth; i++) {
+                        recon[i] =
+                            scanline[i] + paethPredictor(0, precon[i], 0);
+                    }
+                    for (size_t i = bytewidth; i < length; i++) {
+                        recon[i] =
+                            scanline[i] + paethPredictor(recon[i - bytewidth],
+                                                         precon[i],
+                                                         precon[i - bytewidth]);
+                    }
+                } else {
+                    for (size_t i = 0; i < bytewidth; i++) {
+                        recon[i] = scanline[i];
+                    }
+                    for (size_t i = bytewidth; i < length; i++) {
+                        recon[i] = scanline[i] +
+                                   paethPredictor(recon[i - bytewidth], 0, 0);
+                    }
+                }
+                break;
+            default:
+                error = 36;
+                return; // error: unexisting filter type given
+            }
+        }
+        void adam7Pass(unsigned char *out, unsigned char *linen,
+                       unsigned char *lineo, const unsigned char *in,
+                       unsigned long w, size_t passleft, size_t passtop,
+                       size_t spacex, size_t spacey, size_t passw, size_t passh,
+                       unsigned long bpp)
+        { // filter and reposition the pixels
+            // into the output when the image
+            // is Adam7 interlaced. This
+            // function can only do it after
+            // the full image is already
+            // decoded. The out buffer must
+            // have the correct allocated
+            // memory size already.
+            if (passw == 0) {
+                return;
+            }
+            size_t bytewidth = (bpp + 7) / 8,
+                   linelength = 1 + ((bpp * passw + 7) / 8);
+            for (unsigned long y = 0; y < passh; y++) {
+                unsigned char filterType = in[y * linelength],
+                              *prevline = (y == 0) ? nullptr : lineo;
+                unFilterScanline(linen, &in[y * linelength + 1], prevline,
+                                 bytewidth, filterType, (w * bpp + 7) / 8);
+                if (error) {
+                    return;
+                }
+                if (bpp >= 8) {
+                    for (size_t i = 0; i < passw; i++) {
+                        for (size_t b = 0; b < bytewidth;
+                             b++) { // b = current byte of this pixel
+                            out[bytewidth * w * (passtop + spacey * y) +
+                                bytewidth * (passleft + spacex * i) + b] =
+                                linen[bytewidth * i + b];
+                        }
+                    }
+                } else {
+                    for (size_t i = 0; i < passw; i++) {
+                        size_t obp = bpp * w * (passtop + spacey * y) +
+                                     bpp * (passleft + spacex * i),
+                               bp = i * bpp;
+                        for (size_t b = 0; b < bpp; b++) {
+                            setBitOfReversedStream(
+                                obp, out,
+                                readBitFromReversedStream(bp, &linen[0]));
+                        }
+                    }
+                }
+                unsigned char *temp = linen;
+                linen = lineo;
+                lineo = temp; // swap the two buffer pointers "line old" and
+                              // "line new"
+            }
+        }
+        static unsigned long
+        readBitFromReversedStream(size_t &bitp, const unsigned char *bits)
+        {
+            unsigned long result = (bits[bitp >> 3] >> (7 - (bitp & 0x7))) & 1;
+            bitp++;
+            return result;
+        }
+        static unsigned long
+        readBitsFromReversedStream(size_t &bitp, const unsigned char *bits,
+                                   unsigned long nbits)
+        {
+            unsigned long result = 0;
+            for (size_t i = nbits - 1; i < nbits; i--) {
+                result += ((readBitFromReversedStream(bitp, bits)) << i);
+            }
+            return result;
+        }
+        void setBitOfReversedStream(size_t &bitp, unsigned char *bits,
+                                    unsigned long bit)
+        {
+            bits[bitp >> 3] |= (bit << (7 - (bitp & 0x7)));
+            bitp++;
+        }
+        unsigned long read32bitInt(const unsigned char *buffer)
+        {
+            return (buffer[0] << 24) | (buffer[1] << 16) | (buffer[2] << 8) |
+                   buffer[3];
+        }
+        int checkColorValidity(
+            unsigned long colorType,
+            unsigned long bd) // return type is a LodePNG error code
+        {
+            if ((colorType == 2 || colorType == 4 || colorType == 6)) {
+                if (!(bd == 8 || bd == 16)) {
+                    return 37;
+                } else {
+                    return 0;
+                }
+            } else if (colorType == 0) {
+                if (!(bd == 1 || bd == 2 || bd == 4 || bd == 8 || bd == 16)) {
+                    return 37;
+                } else {
+                    return 0;
+                }
+            } else if (colorType == 3) {
+                if (!(bd == 1 || bd == 2 || bd == 4 || bd == 8)) {
+                    return 37;
+                } else {
+                    return 0;
+                }
+            } else {
+                return 31; // unexisting color type
+            }
+        }
+        unsigned long getBpp(const Info &info)
+        {
+            if (info.colorType == 2) {
+                return (3 * info.bitDepth);
+            } else if (info.colorType >= 4) {
+                return (info.colorType - 2) * info.bitDepth;
+            } else {
+                return info.bitDepth;
+            }
+        }
+        int convert(std::vector<unsigned char> &out, const unsigned char *in,
+                    Info &infoIn, unsigned long w, unsigned long h)
+        { // converts from any color type to
+            // 32-bit. return value = LodePNG error
+            // code
+            size_t numpixels = w * h, bp = 0;
+            out.resize(numpixels * 4);
+            unsigned char *out_ =
+                out.empty()
+                    ? nullptr
+                    : &out[0]; // faster if compiled without optimization
+            if (infoIn.bitDepth == 8 && infoIn.colorType == 0) { // greyscale
+                for (size_t i = 0; i < numpixels; i++) {
+                    out_[4 * i + 0] = out_[4 * i + 1] = out_[4 * i + 2] = in[i];
+                    out_[4 * i + 3] =
+                        (infoIn.key_defined && in[i] == infoIn.key_r) ? 0 : 255;
+                }
+            } else if (infoIn.bitDepth == 8 && infoIn.colorType == 2) { // RGB
+                                                                        // color
+                for (size_t i = 0; i < numpixels; i++) {
+                    for (size_t c = 0; c < 3; c++) {
+                        out_[4 * i + c] = in[3 * i + c];
+                    }
+                    out_[4 * i + 3] = (infoIn.key_defined == 1 &&
+                                       in[3 * i + 0] == infoIn.key_r &&
+                                       in[3 * i + 1] == infoIn.key_g &&
+                                       in[3 * i + 2] == infoIn.key_b)
+                                          ? 0
+                                          : 255;
+                }
+            } else if (infoIn.bitDepth == 8 &&
+                       infoIn.colorType == 3) { // indexed color (palette)
+                for (size_t i = 0; i < numpixels; i++) {
+                    if (4U * in[i] >= infoIn.palette.size()) {
+                        return 46;
+                    }
+                    for (size_t c = 0; c < 4; c++) {
+                        out_[4 * i + c] =
+                            infoIn.palette[4 * in[i] + c]; // get rgb colors
+                    }
+                    // from the palette
+                }
+            } else if (infoIn.bitDepth == 8 &&
+                       infoIn.colorType == 4) { // greyscale with alpha
+                for (size_t i = 0; i < numpixels; i++) {
+                    out_[4 * i + 0] = out_[4 * i + 1] = out_[4 * i + 2] =
+                        in[2 * i + 0];
+                    out_[4 * i + 3] = in[2 * i + 1];
+                }
+            } else if (infoIn.bitDepth == 8 && infoIn.colorType == 6) {
+                for (size_t i = 0; i < numpixels; i++) {
+                    for (size_t c = 0; c < 4; c++) {
+                        out_[4 * i + c] = in[4 * i + c]; // RGB with alpha
+                    }
+                }
+            } else if (infoIn.bitDepth == 16 &&
+                       infoIn.colorType == 0) { // greyscale
+                for (size_t i = 0; i < numpixels; i++) {
+                    out_[4 * i + 0] = out_[4 * i + 1] = out_[4 * i + 2] =
+                        in[2 * i];
+                    out_[4 * i + 3] = (infoIn.key_defined &&
+                                       256U * in[i] + in[i + 1] == infoIn.key_r)
+                                          ? 0
+                                          : 255;
+                }
+            } else if (infoIn.bitDepth == 16 &&
+                       infoIn.colorType == 2) { // RGB color
+                for (size_t i = 0; i < numpixels; i++) {
+                    for (size_t c = 0; c < 3; c++) {
+                        out_[4 * i + c] = in[6 * i + 2 * c];
+                    }
+                    out_[4 * i + 3] =
+                        (infoIn.key_defined &&
+                         256U * in[6 * i + 0] + in[6 * i + 1] == infoIn.key_r &&
+                         256U * in[6 * i + 2] + in[6 * i + 3] == infoIn.key_g &&
+                         256U * in[6 * i + 4] + in[6 * i + 5] == infoIn.key_b)
+                            ? 0
+                            : 255;
+                }
+            } else if (infoIn.bitDepth == 16 &&
+                       infoIn.colorType == 4) { // greyscale with alpha
+                for (size_t i = 0; i < numpixels; i++) {
+                    out_[4 * i + 0] = out_[4 * i + 1] = out_[4 * i + 2] =
+                        in[4 * i]; // most significant byte
+                    out_[4 * i + 3] = in[4 * i + 2];
+                }
+            } else if (infoIn.bitDepth == 16 && infoIn.colorType == 6) {
+                for (size_t i = 0; i < numpixels; i++) {
+                    for (size_t c = 0; c < 4; c++) {
+                        out_[4 * i + c] = in[8 * i + 2 * c]; // RGB with alpha
+                    }
+                }
+            } else if (infoIn.bitDepth < 8 &&
+                       infoIn.colorType == 0) { // greyscale
+                for (size_t i = 0; i < numpixels; i++) {
+                    unsigned long value =
+                        (readBitsFromReversedStream(bp, in, infoIn.bitDepth) *
+                         255) /
+                        ((1 << infoIn.bitDepth) -
+                         1); // scale value from 0 to 255
+                    out_[4 * i + 0] = out_[4 * i + 1] = out_[4 * i + 2] =
+                        (unsigned char)(value);
+                    out_[4 * i + 3] =
+                        (infoIn.key_defined && value &&
+                         ((1U << infoIn.bitDepth) - 1U) == infoIn.key_r &&
+                         ((1U << infoIn.bitDepth) - 1U))
+                            ? 0
+                            : 255;
+                }
+            } else if (infoIn.bitDepth < 8 &&
+                       infoIn.colorType == 3) { // palette
+                for (size_t i = 0; i < numpixels; i++) {
+                    unsigned long value =
+                        readBitsFromReversedStream(bp, in, infoIn.bitDepth);
+                    if (4 * value >= infoIn.palette.size()) {
+                        return 47;
+                    }
+                    for (size_t c = 0; c < 4; c++) {
+                        out_[4 * i + c] =
+                            infoIn.palette[4 * value + c]; // get rgb colors
+                    }
+                    // from the palette
+                }
+            }
+            return 0;
+        }
+        unsigned char
+        paethPredictor(short a, short b,
+                       short c) // Paeth predicter, used by PNG filter type 4
+        {
+            short p = a + b - c, pa = p > a ? (p - a) : (a - p),
+                  pb = p > b ? (p - b) : (b - p),
+                  pc = p > c ? (p - c) : (c - p);
+            return (unsigned char)((pa <= pb && pa <= pc) ? a
+                                                          : pb <= pc ? b : c);
+        }
+    };
+    PNG decoder;
+    decoder.decode(out_image, in_png, in_size, convert_to_rgba32);
+    image_width = decoder.info.width;
+    image_height = decoder.info.height;
+    return decoder.error;
+}
+
+} // namespace yage
diff --git a/yage/core/picopng.h b/yage/core/picopng.h
new file mode 100644
index 00000000..095bf68a
--- /dev/null
+++ b/yage/core/picopng.h
@@ -0,0 +1,20 @@
+/* ----------------------------------------------------------------------------
+ * picopng.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <cstdlib>
+#include <vector>
+
+namespace yage
+{
+
+extern int decodePNG(std::vector<unsigned char> &out_image,
+                     unsigned long &image_width, unsigned long &image_height,
+                     const unsigned char *in_png, size_t in_size,
+                     bool convert_to_rgba32 = true);
+
+} // namespace yage
diff --git a/yage/core/resourcemanager.cpp b/yage/core/resourcemanager.cpp
new file mode 100644
index 00000000..f3f9aa20
--- /dev/null
+++ b/yage/core/resourcemanager.cpp
@@ -0,0 +1,21 @@
+/* ----------------------------------------------------------------------------
+ * resourcemanager.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/resourcemanager.h>
+
+namespace yage
+{
+
+TextureCache ResourceManager::texture_cache_;
+
+Texture ResourceManager::getTexture(const std::string &texture_path)
+{
+    return texture_cache_.getTexture(texture_path);
+}
+
+} // namespace yage
diff --git a/yage/core/resourcemanager.h b/yage/core/resourcemanager.h
new file mode 100644
index 00000000..52d98e12
--- /dev/null
+++ b/yage/core/resourcemanager.h
@@ -0,0 +1,33 @@
+
+/* ----------------------------------------------------------------------------
+ * resourcemanager.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef RESOURCE_MANAGER_H
+#define RESOURCE_MANAGER_H
+
+#include "texture.h"
+#include "texturecache.h"
+
+#include <string>
+
+namespace yage
+{
+
+class ResourceManager
+{
+private:
+    static TextureCache texture_cache_;
+
+public:
+    static Texture getTexture(const std::string &texture_path);
+    
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/sprite.cpp b/yage/core/sprite.cpp
new file mode 100644
index 00000000..9ac4dc55
--- /dev/null
+++ b/yage/core/sprite.cpp
@@ -0,0 +1,95 @@
+/* ----------------------------------------------------------------------------
+ * sprite.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/sprite.h>
+#include <yage/base/resourcemanager.h>
+#include <yage/base/vertex.h>
+
+#include <cstddef>
+
+namespace yage
+{
+
+Sprite::~Sprite()
+{
+    if (vbo_id_ != 0) {
+        glDeleteBuffers(1, &vbo_id_);
+    }
+}
+
+void Sprite::init(float x, float y, float width, float height,
+                  const std::string &texture_path)
+{
+    x_ = x;
+    y_ = y;
+    width_ = width;
+    height_ = height;
+    texture_ = ResourceManager::getTexture(texture_path);
+
+    if (vbo_id_ == 0) {
+        glGenBuffers(1, &vbo_id_);
+    }
+
+    Vertex vertex_data[6];
+
+    vertex_data[0].setPosition(x + width, y + height);
+    vertex_data[0].setUv(1.f, 1.f);
+
+    vertex_data[1].setPosition(x, y + height);
+    vertex_data[1].setUv(0.f, 1.f);
+
+    vertex_data[2].setPosition(x, y);
+    vertex_data[2].setUv(0.f, 0.f);
+
+    vertex_data[3].setPosition(x, y);
+    vertex_data[3].setUv(0.f, 0.f);
+
+    vertex_data[4].setPosition(x + width, y + height);
+    vertex_data[4].setUv(1.f, 1.f);
+
+    vertex_data[5].setPosition(x + width, y);
+    vertex_data[5].setUv(1.f, 0.f);
+
+    for (auto &i : vertex_data) {
+        i.setColor(255, 0, 255, 255);
+    }
+
+    vertex_data[1].setColor(0, 255, 255, 255);
+    vertex_data[4].setColor(255, 0, 0, 255);
+
+    glBindBuffer(GL_ARRAY_BUFFER, vbo_id_);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertex_data), vertex_data,
+                 GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+}
+
+void Sprite::draw()
+{
+    glBindTexture(GL_TEXTURE_2D, texture_.id);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo_id_);
+
+    glEnableVertexAttribArray(0);
+    glEnableVertexAttribArray(1);
+    glEnableVertexAttribArray(2);
+
+    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, position));
+    glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, color));
+    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, uv));
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+
+    glDisableVertexAttribArray(2);
+    glDisableVertexAttribArray(1);
+    glDisableVertexAttribArray(0);
+
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+}
+
+} // namespace yage
diff --git a/yage/core/sprite.h b/yage/core/sprite.h
new file mode 100644
index 00000000..725d2160
--- /dev/null
+++ b/yage/core/sprite.h
@@ -0,0 +1,52 @@
+/* ----------------------------------------------------------------------------
+ * sprite.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+/** @file
+  */
+
+#ifndef SPRITE_H
+#define SPRITE_H
+
+#include "texture.h"
+
+#include <glad/glad.h>
+
+#include <string>
+
+namespace yage
+{
+
+/** @deprecated Use SpriteBatch instead
+  */
+class Sprite
+{
+private:
+    float x_;
+    float y_;
+    float width_;
+    float height_;
+    GLuint vbo_id_ = 0;
+    Texture texture_;
+
+public:
+    Sprite() = default;
+    Sprite(const Sprite &) = delete;
+    Sprite(Sprite &&) = delete;
+    ~Sprite();
+
+    Sprite &operator=(const Sprite &) = delete;
+    Sprite &operator=(Sprite &&) = delete;
+
+    void init(float x, float y, float width, float height,
+              const std::string &texture_path);
+    void draw();
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/spritebatch.cpp b/yage/core/spritebatch.cpp
new file mode 100644
index 00000000..aaeec32f
--- /dev/null
+++ b/yage/core/spritebatch.cpp
@@ -0,0 +1,193 @@
+/* ----------------------------------------------------------------------------
+ * spritebatch.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/spritebatch.h>
+
+#include <algorithm>
+#include <stdexcept>
+
+namespace yage
+{
+
+const int SpriteBatch::NUM_VERTICES;
+
+Glyph::Glyph(GLuint texture, float depth, const Vertex &top_left,
+             const Vertex &top_right, const Vertex &bottom_right,
+             const Vertex &bottom_left)
+    : texture_(texture), depth_(depth), top_left_(top_left),
+      top_right_(top_right), bottom_right_(bottom_right),
+      bottom_left_(bottom_left)
+{
+}
+
+RenderBatch::RenderBatch(GLint offset, GLsizei num_vertices, GLuint texture)
+    : num_vertices_(num_vertices), offset_(offset), texture_(texture)
+{
+}
+
+SpriteBatch::SpriteBatch() = default;
+
+SpriteBatch::~SpriteBatch()
+{
+    if (vao_ != 0) {
+        glDeleteVertexArrays(1, &vao_);
+    }
+
+    if (vbo_ != 0) {
+        glDeleteVertexArrays(1, &vbo_);
+    }
+}
+
+void SpriteBatch::init()
+{
+    createVertexArray();
+}
+
+void SpriteBatch::begin()
+{
+    glyphs_.clear();
+    glyph_ptrs_.clear();
+    render_batches_.clear();
+}
+
+void SpriteBatch::end()
+{
+    sortGlyphs();
+    createRenderBatches();
+}
+
+void SpriteBatch::draw(const yage::Vector4f &destination_rect,
+                       const yage::Vector4f &uv_rect, GLuint texture,
+                       const Color &color, float depth)
+{
+    Vertex top_left, top_right, bottom_right, bottom_left;
+
+    top_left.color = color;
+    top_left.setPosition(destination_rect.x,
+                         destination_rect.y + destination_rect.w);
+    top_left.setUv(uv_rect.x, uv_rect.y + uv_rect.w);
+
+    top_right.color = color;
+    top_right.setPosition(destination_rect.x + destination_rect.z,
+                          destination_rect.y + destination_rect.w);
+    top_right.setUv(uv_rect.x + uv_rect.z, uv_rect.y + uv_rect.w);
+
+    bottom_right.color = color;
+    bottom_right.setPosition(destination_rect.x + destination_rect.z,
+                             destination_rect.y);
+    bottom_right.setUv(uv_rect.x + uv_rect.z, uv_rect.y);
+
+    bottom_left.color = color;
+    bottom_left.setPosition(destination_rect.x, destination_rect.y);
+    bottom_left.setUv(uv_rect.x, uv_rect.y);
+
+    // deal with fragmenting by creating vector of pointers
+    glyphs_.emplace_back(texture, depth, top_left, top_right, bottom_right,
+                         bottom_left);
+    glyph_ptrs_.push_back(&glyphs_.back());
+}
+
+void SpriteBatch::render()
+{
+    glBindVertexArray(vao_);
+    for (auto &&batch : render_batches_) {
+        glBindTexture(GL_TEXTURE_2D, batch.texture());
+        glDrawArrays(GL_TRIANGLES, batch.offset(), batch.num_vertices());
+    }
+    glBindVertexArray(0);
+}
+
+void SpriteBatch::createVertexArray()
+{
+    if (vao_ == 0) {
+        glGenVertexArrays(1, &vao_);
+        if (vao_ == 0) {
+            throw std::runtime_error("glGenVertexArrays failed");
+        }
+    }
+    // bind vertex array object
+    glBindVertexArray(vao_);
+
+    if (vbo_ == 0) {
+        glGenBuffers(1, &vbo_);
+        if (vbo_ == 0) {
+            throw std::runtime_error("glGenBuffers failed");
+        }
+    }
+    // bind vertex buffer object
+    glBindBuffer(GL_ARRAY_BUFFER, vbo_);
+
+    // enable vertex attribute arrays
+    glEnableVertexAttribArray(0);
+    glEnableVertexAttribArray(1);
+    glEnableVertexAttribArray(2);
+
+    // set the vertex attribute pointers
+    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, position));
+    glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, color));
+    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
+                          (void *)offsetof(Vertex, uv));
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+
+    // unbind vertex array object
+    glBindVertexArray(0);
+}
+
+void SpriteBatch::createRenderBatches()
+{
+    std::vector<Vertex> vertices;
+    if (glyph_ptrs_.empty()) {
+        return;
+    }
+
+    render_batches_.reserve(glyph_ptrs_.size() * NUM_VERTICES);
+
+    for (int i = 0; i < (int)glyph_ptrs_.size(); ++i) {
+        if (i == 0 || (i > 0 && (glyph_ptrs_[i]->texture() !=
+                                 glyph_ptrs_[i - 1]->texture()))) {
+            render_batches_.emplace_back(i * NUM_VERTICES, NUM_VERTICES,
+                                         glyph_ptrs_[i]->texture());
+        } else {
+            render_batches_.back().num_vertices_ += NUM_VERTICES;
+        }
+
+        vertices.push_back(glyph_ptrs_[i]->bottom_left());
+        vertices.push_back(glyph_ptrs_[i]->top_left());
+        vertices.push_back(glyph_ptrs_[i]->top_right());
+        vertices.push_back(glyph_ptrs_[i]->bottom_left());
+        vertices.push_back(glyph_ptrs_[i]->bottom_right());
+        vertices.push_back(glyph_ptrs_[i]->top_right());
+
+        // bind vbo
+        glBindBuffer(GL_ARRAY_BUFFER, vbo_);
+        // orphan the buffer
+        glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(Vertex), nullptr,
+                     GL_DYNAMIC_DRAW);
+        // upload the data
+        glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.size() * sizeof(Vertex),
+                        vertices.data());
+        // unbind buffer
+        glBindBuffer(GL_ARRAY_BUFFER, 0);
+    }
+}
+
+void SpriteBatch::sortGlyphs()
+{
+    // sort using introsort or quicksort
+    std::sort(glyph_ptrs_.begin(), glyph_ptrs_.end(),
+              [](Glyph *a, Glyph *b) -> bool {
+                  if (a->depth() == b->depth()) {
+                      return a->texture() < b->texture();
+                  }
+                  return a->depth() < b->depth();
+              });
+}
+
+} // namespace yage
diff --git a/yage/core/spritebatch.h b/yage/core/spritebatch.h
new file mode 100644
index 00000000..953055f6
--- /dev/null
+++ b/yage/core/spritebatch.h
@@ -0,0 +1,110 @@
+/* ----------------------------------------------------------------------------
+ * spritebatch.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+/** @file
+ */
+
+#ifndef YAGE_SPRITE_BATCH_H
+#define YAGE_SPRITE_BATCH_H
+
+#include "vertex.h"
+
+#include <glad/glad.h>
+#include <glm/glm.hpp>
+#include <yage/math/matrix.h>
+
+#include <vector>
+
+namespace yage
+{
+
+class SpriteBatch;
+
+/** Glyph with information of the texture.
+ */
+class Glyph
+{
+private:
+    GLuint texture_;
+    float depth_;
+    Vertex top_left_;
+    Vertex top_right_;
+    Vertex bottom_right_;
+    Vertex bottom_left_;
+
+public:
+    Glyph(GLuint texture, float depth, const Vertex &top_left,
+          const Vertex &top_right, const Vertex &bottom_right,
+          const Vertex &bottom_left);
+
+    GLuint texture() const { return texture_; }
+    float depth() const { return depth_; }
+    Vertex top_left() const { return top_left_; }
+    Vertex top_right() const { return top_right_; }
+    Vertex bottom_right() const { return bottom_right_; }
+    Vertex bottom_left() const { return bottom_left_; }
+};
+
+class RenderBatch
+{
+    friend SpriteBatch;
+
+private:
+    GLsizei num_vertices_;
+    GLint offset_;
+    GLuint texture_;
+
+public:
+    RenderBatch(GLint offset, GLsizei num_vertices, GLuint texture);
+
+    GLint offset() const { return offset_; }
+    GLsizei num_vertices() const { return num_vertices_; }
+    GLuint texture() const { return texture_; }
+};
+
+class SpriteBatch
+{
+public:
+    static const int NUM_VERTICES = 6;
+
+private:
+    GLuint vbo_ = 0;
+    GLuint vao_ = 0;
+    std::vector<Glyph> glyphs_;
+    std::vector<Glyph *> glyph_ptrs_;
+    std::vector<RenderBatch> render_batches_;
+
+public:
+    SpriteBatch();
+    SpriteBatch(const SpriteBatch &) = delete;
+    SpriteBatch(SpriteBatch &&) = delete;
+    ~SpriteBatch();
+
+    SpriteBatch &operator=(const SpriteBatch &) = delete;
+    SpriteBatch &operator=(SpriteBatch &&) = delete;
+
+    // initialize vaos and vbos
+    void init();
+    void begin();
+    void end();
+    // adds a sprite to the sprite batch to be rendered later
+    void draw(const yage::Vector4f &destination_rect,
+              const yage::Vector4f &uv_rect, GLuint texture, const Color &color,
+              float depth);
+    // render the batch
+    void render();
+
+private:
+    void createVertexArray();
+    void createRenderBatches();
+    void sortGlyphs();
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/spritesheet.cpp b/yage/core/spritesheet.cpp
new file mode 100644
index 00000000..5c3499cc
--- /dev/null
+++ b/yage/core/spritesheet.cpp
@@ -0,0 +1,85 @@
+/* ----------------------------------------------------------------------------
+ * spritesheet.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com>
+ * MIT License, see LICENSE file for more details.
+ * ----------------------------------------------------------------------------
+ */
+
+/** @file
+ */
+
+#include "spritesheet.h"
+
+#include <cassert>
+#include <fstream>
+#include <sstream>
+#include <stdexcept>
+
+#include <rapidjson/document.h>
+#include <yage/base/imageloader.h>
+
+using namespace std;
+using namespace rapidjson;
+using namespace yage::details;
+
+namespace yage
+{
+
+SpriteSheet::SpriteSheet(string pngFileName, string jsonFileName)
+{
+    int jsonWidth, jsonHeight;
+    fileLocations_ =
+        parseJson(jsonWidth, jsonHeight, fileContent(jsonFileName));
+    texture_ = ImageLoader::loadPng(pngFileName);
+
+    if (texture_.width != jsonWidth)
+        throw runtime_error("JSON width does not match texture width");
+    if (texture_.height != jsonHeight) 
+        throw runtime_error("JSON height does not match texture height");
+}
+
+string SpriteSheet::fileContent(string jsonFileName) const
+{
+    ifstream inputFile(jsonFileName);
+
+    stringstream stream;
+    stream << inputFile.rdbuf();
+
+    return stream.str();
+}
+
+SpriteMap SpriteSheet::parseJson(int &width, int &height,
+                                 string jsonContent) const
+{
+    SpriteMap spriteMap;
+    Document jsonAtlas;
+    jsonAtlas.Parse(jsonContent.c_str());
+
+    width = jsonAtlas["width"].GetInt();
+    height = jsonAtlas["height"].GetInt();
+
+    for (auto &texture : jsonAtlas["sprites"].GetObject()) {
+        Coordinate coord;
+        for (auto &value : texture.value.GetObject()) {
+            string keyName{value.value.GetString()};
+            int keyValue{value.value.GetInt()};
+            if (keyName == "x") {
+                coord.x = keyValue;
+            } else if (keyName == "y") {
+                coord.y = keyValue;
+            } else if (keyName == "width") {
+                coord.width = keyValue;
+            } else if (keyName == "height") {
+                coord.height = keyValue;
+            } else {
+                throw runtime_error("JSON key incorrect: " + keyName);
+            }
+        }
+        spriteMap[texture.name.GetString()] = coord;
+    }
+
+    return spriteMap;
+}
+
+} // namespace yage
diff --git a/yage/core/spritesheet.h b/yage/core/spritesheet.h
new file mode 100644
index 00000000..2ead0ba1
--- /dev/null
+++ b/yage/core/spritesheet.h
@@ -0,0 +1,64 @@
+/* ----------------------------------------------------------------------------
+ * spritesheet.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com>
+ * MIT License, see LICENSE file for more details.
+ * ----------------------------------------------------------------------------
+ */
+
+/** @file
+ */
+
+#ifndef YAGE_SPRITESHEET_H
+#define YAGE_SPRITESHEET_H
+
+#include "texture.h"
+
+#include <rapidjson/reader.h>
+
+#include <map>
+#include <string>
+
+namespace yage
+{
+
+namespace details
+{
+
+struct Coordinate {
+    int x;
+    int y;
+    int width;
+    int height;
+
+    Coordinate() = default;
+
+    Coordinate(int x_i, int y_i, int width_i, int height_i)
+        : x(x_i), y(y_i), width(width_i), height(height_i)
+    {
+    }
+};
+
+typedef std::map<std::string, details::Coordinate> SpriteMap;
+
+} // namespace details
+
+class SpriteSheet
+{
+public:
+    SpriteSheet(std::string pngFileName, std::string jsonFileName);
+
+    void sprite(std::string spriteName) const;
+    std::string fileContent(std::string jsonFileName) const;
+
+private:
+    Texture texture_;
+    details::SpriteMap fileLocations_;
+
+    details::SpriteMap parseJson(int &width, int &height,
+                                 std::string jsonContent) const;
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/texture.h b/yage/core/texture.h
new file mode 100644
index 00000000..82b7dde3
--- /dev/null
+++ b/yage/core/texture.h
@@ -0,0 +1,32 @@
+/* ----------------------------------------------------------------------------
+ * texture.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef GL_TEXTURE_H
+#define GL_TEXTURE_H
+
+#include <glad/glad.h>
+
+namespace yage
+{
+
+struct Texture {
+    GLuint id;
+    int width;
+    int height;
+
+    Texture() = default;
+
+    Texture(GLuint id_i, int width_i, int height_i)
+        : id(id_i), width(width_i), height(height_i)
+    {
+    }
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/texturecache.cpp b/yage/core/texturecache.cpp
new file mode 100644
index 00000000..628f3604
--- /dev/null
+++ b/yage/core/texturecache.cpp
@@ -0,0 +1,28 @@
+/* ----------------------------------------------------------------------------
+ * texturecache.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include <yage/base/texturecache.h>
+#include <yage/base/imageloader.h>
+
+namespace yage
+{
+
+Texture TextureCache::getTexture(const std::string &texture_path)
+{
+    auto itr = texture_map_.find(texture_path);
+
+    if (itr == texture_map_.end()) {
+        Texture new_texture = ImageLoader::loadPng(texture_path);
+        texture_map_.insert(make_pair(texture_path, new_texture));
+        return new_texture;
+    }
+
+    return itr->second;
+}
+
+} // namespace yage
diff --git a/yage/core/texturecache.h b/yage/core/texturecache.h
new file mode 100644
index 00000000..b28349ec
--- /dev/null
+++ b/yage/core/texturecache.h
@@ -0,0 +1,33 @@
+/* ----------------------------------------------------------------------------
+ * texturecache.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef TEXTURE_CACHE_H
+#define TEXTURE_CACHE_H
+
+#include "texture.h"
+
+#include <unordered_map>
+
+namespace yage
+{
+
+class TextureCache
+{
+private:
+    std::unordered_map<std::string, Texture> texture_map_;
+
+public:
+    TextureCache() = default;
+
+    Texture getTexture(const std::string &texture_path);
+    Texture getTextureFromSpriteSheet();
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/vertex.h b/yage/core/vertex.h
new file mode 100644
index 00000000..586e8190
--- /dev/null
+++ b/yage/core/vertex.h
@@ -0,0 +1,84 @@
+/* ----------------------------------------------------------------------------
+ * vertex.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#ifndef VERTEX_H
+#define VERTEX_H
+
+#include <glad/glad.h>
+
+namespace yage
+{
+
+struct Position {
+    float x;
+    float y;
+
+    Position() = default;
+
+    Position(float x_, float y_) : x(x_), y(y_) {}
+};
+
+struct Color {
+    GLubyte r;
+    GLubyte g;
+    GLubyte b;
+    GLubyte a;
+
+    Color() = default;
+
+    Color(GLubyte r_, GLubyte g_, GLubyte b_, GLubyte a_)
+        : r(r_), g(g_), b(b_), a(a_)
+    {
+    }
+};
+
+struct UV {
+    float u;
+    float v;
+
+    UV() = default;
+
+    UV(float u_, float v_) : u(u_), v(v_) {}
+};
+
+struct Vertex {
+    Position position;
+    Color color;
+    UV uv;
+
+    Vertex() = default;
+
+    Vertex(const Position &position_, const Color &color_, const UV &uv_)
+        : position(position_), color(color_), uv(uv_)
+    {
+    }
+
+    void setPosition(float x, float y)
+    {
+        position.x = x;
+        position.y = y;
+    }
+
+    void setColor(GLubyte r, GLubyte g, GLubyte b, GLubyte a)
+    {
+        color.r = r;
+        color.g = g;
+        color.b = b;
+        color.a = a;
+    }
+
+    void setUv(float u, float v)
+    {
+        uv.u = u;
+        uv.v = v;
+    }
+};
+
+} // namespace yage
+
+#endif
diff --git a/yage/core/window.cpp b/yage/core/window.cpp
new file mode 100644
index 00000000..9774bf9e
--- /dev/null
+++ b/yage/core/window.cpp
@@ -0,0 +1,103 @@
+/* ----------------------------------------------------------------------------
+ * window.cpp
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+#include "window.h"
+
+#include <stdexcept>
+
+
+
+namespace yage
+{
+
+void key_callback(GLFWwindow *window, int key, int scanCode, int action, int mods)
+{
+    if(key == GLFW_KEY_E && action == GLFW_PRESS) {
+        glClearColor(0.5f, 0.f, 0.f, 1.f);
+    } else {
+        glClearColor(0.f, 0.5f, 0.f, 1.f);
+    }
+}
+
+Window::Window() = default;
+
+Window::~Window()
+{
+    glfwDestroyWindow(window_);
+    glfwTerminate();
+}
+
+void Window::create(std::string window_name, int width, int height)
+{
+    if(glfwInit() == GLFW_FALSE) {
+        throw std::runtime_error("GLFW Initialisation failed");
+    }
+
+    glfwWindowHint(GLFW_VERSION_MAJOR, 4);
+    glfwWindowHint(GLFW_VERSION_MINOR, 5);
+
+    window_ =
+        glfwCreateWindow(width, height, window_name.c_str(), nullptr, nullptr);
+    if (window_ == nullptr) {
+        throw std::runtime_error("GLFW Window creation failed");
+    }
+
+    // initialize the gl context
+    glfwMakeContextCurrent(window_);
+
+    // initialize glad
+    gladLoadGLLoader((GLADloadproc) glfwGetProcAddress);
+
+    // set key callback
+    glfwSetKeyCallback(window_, key_callback);
+
+    // set vsync on
+    glfwSwapInterval(1);
+
+    // set the clear color to black
+    glClearColor(0.f, 0.5f, 0.f, 1.f);
+    // set alpha blending
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    // set the clear depth
+    glClearDepth(1.f);
+}
+
+void Window::swapBuffer()
+{
+    // swap the window buffer
+    glfwSwapBuffers(window_);
+}
+
+void Window::clearBuffer()
+{
+    // clears buffer with clear color
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+}
+
+void Window::hide()
+{
+    glfwHideWindow(window_);
+}
+
+void Window::show()
+{
+    glfwShowWindow(window_);
+}
+
+bool Window::shouldClose()
+{
+    return glfwWindowShouldClose(window_);
+}
+
+void Window::pollEvents() const
+{
+    glfwPollEvents();
+}
+
+} // namespace yage
diff --git a/yage/core/window.h b/yage/core/window.h
new file mode 100644
index 00000000..84ba8303
--- /dev/null
+++ b/yage/core/window.h
@@ -0,0 +1,65 @@
+/* ----------------------------------------------------------------------------
+ * window.h
+ *
+ * Copyright (c) 2017 Yann Herklotz Grave <ymherklotz@gmail.com> -- MIT License
+ * See file LICENSE for more details
+ * ----------------------------------------------------------------------------
+ */
+
+/** @file
+  */
+
+#ifndef WINDOW_H
+#define WINDOW_H
+
+#include <glad/glad.h>
+
+#include <GLFW/glfw3.h>
+
+#include <string>
+
+namespace yage
+{
+
+// window flags that can change it's appearance
+enum WindowFlags : unsigned {
+    SHOWN = 0x1,
+    HIDDEN = 0x2,
+    FULLSCREEN = 0x4,
+    BORDERLESS = 0x8,
+};
+
+// window wrapper around GLFWwindow pointer
+class Window
+{
+private:
+    /// window handle
+    GLFWwindow *window_ = nullptr;
+
+public:
+    Window();
+    Window(const Window &) = delete;
+    Window(Window &&) = delete;
+    /// destroys the window handle
+    ~Window();
+
+    Window &operator=(const Window &) = delete;
+    Window &operator=(Window &&) = delete;
+
+    /// create the window, initialize the handle and update the width and height
+    void create(std::string window_name, int width, int height);
+    /// swap the buffer
+    void swapBuffer();
+    /// clear buffer
+    void clearBuffer();
+    /// hide windowProc
+    void hide();
+    /// show window
+    void show();
+    bool shouldClose();
+    void pollEvents() const;
+};
+
+} // namespace yage
+
+#endif