SDL表面像素格式轉換

Question

我想將一個由IMG_Load（）加載的SDL_Surface轉換爲OpenGL紋理的其他像素格式（rgba8）。我怎樣才能做到這一點？ 我已閱讀有關SDL_ConvertSurface（）在文檔中，但我想不通，如何把它放在一起。

Answer 1

給"How To Load an OpenGL Texture from an SDL_Surface"一個鏡頭：

GLuint texture;   // This is a handle to our texture object 
SDL_Surface *surface; // This surface will tell us the details of the image 
GLenum texture_format; 
GLint nOfColors; 

if((surface = SDL_LoadBMP("image.bmp"))) 
{ 
    // Check that the image's width is a power of 2 
    if((surface->w & (surface->w - 1)) != 0) 
    { 
     printf("warning: image.bmp's width is not a power of 2\n"); 
    } 

    // Also check if the height is a power of 2 
    if((surface->h & (surface->h - 1)) != 0) 
    { 
     printf("warning: image.bmp's height is not a power of 2\n"); 
    } 

    // get the number of channels in the SDL surface 
    nOfColors = surface->format->BytesPerPixel; 
    if(nOfColors == 4)  // contains an alpha channel 
    { 
     if(surface->format->Rmask == 0x000000ff) 
      texture_format = GL_RGBA; 
     else 
      texture_format = GL_BGRA; 
    } 
    else if(nOfColors == 3)  // no alpha channel 
    { 
     if(surface->format->Rmask == 0x000000ff) 
      texture_format = GL_RGB; 
     else 
      texture_format = GL_BGR; 
    } 
    else 
    { 
     printf("warning: the image is not truecolor.. this will probably break\n"); 
     // this error should not go unhandled 
    } 

    // Have OpenGL generate a texture object handle for us 
    glGenTextures(1, &texture); 

    // Bind the texture object 
    glBindTexture(GL_TEXTURE_2D, texture); 

    // Set the texture's stretching properties 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 

    // Edit the texture object's image data using the information SDL_Surface gives us 
    glTexImage2D 
     (
     GL_TEXTURE_2D, 
     0, 
     nOfColors, 
     surface->w, 
     surface->h, 
     0, 
     texture_format, 
     GL_UNSIGNED_BYTE, 
     surface->pixels 
     ); 
} 
else 
{ 
    printf("SDL could not load image.bmp: %s\n", SDL_GetError()); 
    SDL_Quit(); 
    return 1; 
}  

// Free the SDL_Surface only if it was successfully created 
if(surface) 
{ 
    SDL_FreeSurface(surface); 
}