如何在Free Pascal中使用SDL2从表面或纹理读取给定坐标x和y处特定像素的RGBA值?
var spriteSheetTexture: PSDL_texture; pixel: ^UInt8; pixelCnt: byte; SDLRect: TSDL_rect; spriteSheetSurface:=SDL_loadBMP(PChar('spr4\sprite sheets\spr'+fVal(spriteSheetNum)+'.spr')); SDLRect.x:=0; SDLRect.y:=0; SDLRect.w:=1; SDLRect.h:=1; SDL_renderReadPixels(SDLRenderer, @SDLRect, 0, pixel, spriteSheetSurface^.pitch); for pixelCnt:=0 to 3 do writeLn(pixel[pixelCnt]);
实际上,它似乎不起作用。无论我读取哪个像素,pixel都会为每个索引返回零。