我目前正在使用纯C方法与SDL（及其官方的额外库，如SDL_image）和OpenGL开发一个非常简单的游戏。但现在我遇到了一些问题，不知道为什么会这样：绘制时颜色全都偏离了。我目前在Mac上运行程序，但是如果我记得正确的话，在Windows上运行时颜色更接近正确，但仍然存在一些奇怪的问题（例如，一个纯白色多边形绘制成黄色）。
目前在我的Mac上，所有加载为png文件的图像颜色都有点偏差，并且一个纯白色的多边形被绘制成深绿色。还有一些图像被绘制成纯白色。如果我记得正确的话，在Windows上，图像被正确绘制，但是之前提到的白色多边形是黄色的。现在我将发布初始化、加载等相关代码。
现在我将展示实际将图像加载到内存中的代码：
目前在我的Mac上，所有加载为png文件的图像颜色都有点偏差，并且一个纯白色的多边形被绘制成深绿色。还有一些图像被绘制成纯白色。如果我记得正确的话，在Windows上，图像被正确绘制，但是之前提到的白色多边形是黄色的。现在我将发布初始化、加载等相关代码。
int main( int argc, char *argv[] ) {
//initializing various OpenGL attributes with SDL utilities
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 ); //needs for 3D
SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 ); //only needed for systems other than mac osx
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 );
/* Set 640x480 video mode */
screen=SDL_SetVideoMode(screen_width,screen_height, 8, videoflags );
if (screen == NULL) {
fprintf(stderr, "Couldn't set %dx%dx%d video mode: %s\n",
screen_width, screen_height,
video_info->vfmt->BitsPerPixel, SDL_GetError());
exit(2);
}
glShadeModel( GL_SMOOTH );
glClearColor( 0.3f, 0.3f, 0.3f, 0 );
glViewport( 0, 0, (GLsizei)screen->w, (GLsizei)screen->h );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluOrtho2D( 0.0f, screen->w, 0.0f, screen->h );
/*glEnable( GL_BLEND );
glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );*/
glEnable( GL_ALPHA_TEST );
glAlphaFunc( GL_GREATER, 0.1f );
// Some basic initialization stuff goes here
// Assume infinite while loop goes here, except when esc is pressed
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glEnable( GL_TEXTURE_2D );
draw_gui();
// Things get drawn here
glDisable( GL_TEXTURE_2D );
SDL_GL_SwapBuffers();
SDL_Delay( 10 );
// End of while loop, clean up, etc.
}
现在我将展示实际将图像加载到内存中的代码：
Sprite *gen_sprite( char *file ) {
SDL_Surface *buffer = IMG_Load( file );
if( buffer == NULL ) {
fprintf( stderr, "Could not load image '%s'\n for reason: %s\n",
file, IMG_GetError() );
exit( 3 );
}
return gen_sprite_from( buffer );
}
Sprite *gen_sprite_from( SDL_Surface *buffer ) {
Sprite *sprite;
GLuint texture;
if( buffer == NULL ) {
fprintf( stderr, "NULL surface passed to gen_sprite_from." );
exit( 3 );
}
texture = gen_Gl_texture_from( buffer );
if( ( sprite = malloc( sizeof( Sprite ) ) ) == NULL ) {
fprintf( stderr, "Malloc failed to allocate space for a Sprite.\n" );
exit( 1 );
}
if( ( sprite->tex = malloc( sizeof( GLuint ) ) ) == NULL ) {
fprintf( stderr, "Malloc failed to allocate space for a GLuint.\n" );
exit( 1 );
}
sprite->tex[ 0 ] = texture;
sprite->original = buffer;
sprite->is_animation = 0;
sprite->cur_frame = 0;
sprite->cur_time = 0;
sprite->num_frames = 1;
sprite->frame_time = NULL;
return sprite;
}
Uint32 gen_Gl_texture_from( SDL_Surface *buffer ) {
GLuint texture;
SDL_Surface *temp;
glPixelStorei( GL_UNPACK_ALIGNMENT, 4 );
glGenTextures( 1, &texture );
temp = SDL_CreateRGBSurface( SDL_SWSURFACE, buffer->w, buffer->h, 32,
0x000000FF, 0x0000FF00, 0x00FF0000, 0xFF000000 );
SDL_SetAlpha( buffer, 0, SDL_ALPHA_OPAQUE );
SDL_BlitSurface( buffer, NULL, temp, NULL );
glBindTexture( GL_TEXTURE_2D, texture );
//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE );
gluBuild2DMipmaps( GL_TEXTURE_2D, 4,
temp->w, temp->h,
GL_RGBA, GL_UNSIGNED_BYTE,
temp->pixels );
SDL_FreeSurface( temp );
// This just creates white blocks instead of actually loading textures
//glPixelStorei( GL_UNPACK_ALIGNMENT, buffer->format->BytesPerPixel );
//glGenTextures( 1, &texture );
//glBindTexture( GL_TEXTURE_2D, texture );
//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
//glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
//glTexImage2D( GL_TEXTURE_2D, 0, mask_order, buffer->w, buffer->h, 0,
// mask_order, GL_UNSIGNED_BYTE, buffer->pixels );
return texture;
}
现在，我相信所有与颜色偏差有关的代码都已经发布。绘图代码非常简单，只需要进行平移或旋转等操作，绑定纹理，然后使用纹理坐标和顶点进行简单的开始/结束块。如果有人能告诉我为什么颜色会偏差，并让我知道一种在跨平台方式下确保颜色始终正确的好方法（我计划在所有平台上构建，这也是我使用SDL的原因之一），我将不胜感激。
screen=SDL_SetVideoMode(screen_width,screen_height, 8, videoflags );这会设置8位颜色...你似乎想要32位，是吗？ - Orkatemp = SDL_CreateRGBSurface( SDL_SWSURFACE, buffer->w, buffer->h, buffer->format->BitsPerPixel, buffer->format->Rmask, buffer->format->Gmask, buffer->format->Bmask, buffer->format->Amask);代替temp = SDL_CreateRGBSurface( SDL_SWSURFACE, buffer->w, buffer->h, 32, 0x000000FF, 0x0000FF00, 0x00FF0000, 0xFF000000 );。如果您没有将缓冲区设置为启用alpha通道的表面，则可能会在初始alpha渲染时出现问题。 - OrkaglClearColor( 0.3f, 0.3f, 0.3f, 0 );is asking for a grey of 0.3f, fair enough, but that 0 at the end is asking for one that is completely transparent. You probably want one that is opaque...glClearColor( 0.3f, 0.3f, 0.3f, 1.0f );- burito