# 将 stb_image 替换为 SDL_image 完整计划

## 概述
将项目中的 stb_image 完全替换为 SDL_image，以解决 Switch 平台兼容性问题。

## 修改文件清单

### 1. 平台配置文件（3个文件）
- `platform/mingw.lua` - Windows/Mingw 配置
- `platform/linux.lua` - Linux 配置  
- `platform/switch.lua` - Switch 配置

### 2. 核心代码文件（1个文件）
- `Frostbite2D/src/frostbite2D/graphics/texture.cpp` - 纹理加载实现

## 详细修改方案

### 修改 1: platform/mingw.lua
**变更**: 添加 SDL_image 依赖
```lua
-- 修改前
add_requires("libsdl2", {configs = {shared = true}})
add_requires("glm")

-- 修改后
add_requires("libsdl2", {configs = {shared = true}})
add_requires("libsdl2_image", {configs = {shared = true}})
add_requires("glm")

-- 在 add_packages 部分添加
add_packages("libsdl2")
add_packages("libsdl2_image")
add_packages("glm")
```

### 修改 2: platform/linux.lua
**变更**: 添加 SDL_image 依赖
```lua
-- 修改前
add_requires("libsdl2", {configs = {shared = true,wayland = true}})
add_requires("glm")

-- 修改后
add_requires("libsdl2", {configs = {shared = true,wayland = true}})
add_requires("libsdl2_image")
add_requires("glm")

-- 在 add_packages 部分添加
add_packages("libsdl2")
add_packages("libsdl2_image")
add_packages("glm")
```

### 修改 3: platform/switch.lua
**变更**: 添加 SDL2_image 库链接
```lua
-- 修改前
add_syslinks("SDL2_mixer", "SDL2", "opusfile", "opus", "vorbisidec", "ogg",
                     "modplug", "mpg123", "FLAC", "GLESv2", "EGL", "glapi", "drm_nouveau",
                     {public = true})

-- 修改后
add_syslinks("SDL2_mixer", "SDL2_image", "SDL2", "opusfile", "opus", "vorbisidec", "ogg",
                     "modplug", "mpg123", "FLAC", "GLESv2", "EGL", "glapi", "drm_nouveau",
                     {public = true})
```

### 修改 4: texture.cpp
**变更**: 完全重写 `loadFromFile` 函数，使用 SDL_image
```cpp
#include <cstdio>
#include <cstdlib>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>

// 移除所有 stb_image 相关的定义和 include
// #define STB_IMAGE_IMPLEMENTATION
// #include <stb/stb_image.h>

namespace frostbite2D {

Ptr<Texture> Texture::loadFromFile(const std::string& path) {
  Asset& asset = Asset::get();
  std::string resolvedPath = asset.resolveAssetPath(path);
  std::vector<uint8> fileData;
  
  SDL_Log("LoadQ");
  if (!asset.readBinaryFile(path, fileData)) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to read texture file: %s", resolvedPath.c_str());
    return nullptr;
  }
  SDL_Log("LoadQ1: file size = %zu bytes", fileData.size());
  
  if (fileData.empty()) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Texture file is empty: %s", resolvedPath.c_str());
    return nullptr;
  }
  
  // 使用 SDL_image 从内存加载
  SDL_RWops* rw = SDL_RWFromConstMem(fileData.data(), static_cast<int>(fileData.size()));
  if (!rw) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to create RWops: %s", SDL_GetError());
    return nullptr;
  }
  
  SDL_Surface* surface = IMG_Load_RW(rw, 1);
  if (!surface) {
    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to load image: %s", IMG_GetError());
    SDL_FreeRW(rw);
    return nullptr;
  }
  
  SDL_Log("LoadQ2: %dx%d, format: %d", surface->w, surface->h, surface->format->format);
  
  // 确定格式
  GLenum format;
  int channels;
  if (surface->format->BytesPerPixel == 4) {
    format = GL_RGBA;
    channels = 4;
  } else {
    format = GL_RGB;
    channels = 3;
  }
  
  int width = surface->w;
  int height = surface->h;
  
  uint32_t textureID;
  glGenTextures(1, &textureID);
  glBindTexture(GL_TEXTURE_2D, textureID);
  
  glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, surface->pixels);
  
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  
  glBindTexture(GL_TEXTURE_2D, 0);
  
  SDL_FreeSurface(surface);
  
  auto texture = Ptr<Texture>(new Texture(width, height, textureID));
  texture->path_ = resolvedPath;
  texture->channels_ = channels;
  
  SDL_Log("Loaded texture: %s (%dx%d, %d channels)", resolvedPath.c_str(), width, height, channels);
  
  return texture;
}

// ... 其余函数保持不变
}
```

## 实施步骤

1. 修改 3 个平台配置文件，添加 SDL_image 依赖
2. 修改 texture.cpp，替换 stb_image 为 SDL_image
3. 清理 xmake 缓存
4. 重新编译项目
5. 测试所有平台

## 注意事项

- SDL_image 支持的图片格式包括: PNG, JPEG, BMP, GIF, TIFF, WebP 等
- 确保所有平台都能正确链接 SDL_image 库
- Switch 平台的 devkitPro/portlibs 应该已经包含 SDL2_image