Added texture packer for automatically creating texture atlas on build.

private/texture_packer/packer.hpp

@@ -0,0 +1,47 @@
+
+#pragma once
+
+#if !defined(SDL_GPU_TEST_PRIVATE_TEXTURE_PACKER_PACKER_HPP_INCLUDED)
+#define SDL_GPU_TEST_PRIVATE_TEXTURE_PACKER_PACKER_HPP_INCLUDED 1
+
+#include <filesystem>
+#include <vector>
+
+namespace fs = std::filesystem;
+
+namespace sdl_gpu_test
+{
+struct FreeDeleter
+{
+    void operator()(void* ptr) noexcept
+    {
+        std::free(ptr);
+    }
+};
+
+class Packer
+{
+private:
+    struct Pixel
+    {
+        std::uint8_t r;
+        std::uint8_t g;
+        std::uint8_t b;
+        std::uint8_t a;
+    };
+    struct ImageData
+    {
+        std::string name;
+        std::unique_ptr<Pixel[], FreeDeleter> data;
+        unsigned width;
+        unsigned height;
+    };
+
+    std::vector<ImageData> mImages;
+public:
+    void addImage(const fs::path& path);
+    void pack(const fs::path& outputPath);
+};
+} // namespace sdl_gpu_test
+
+#endif // !defined(SDL_GPU_TEST_PRIVATE_TEXTURE_PACKER_PACKER_HPP_INCLUDED)