Haskell光泽:将图片渲染到位图

Question

我想访问窗口显示内容的像素数据,但我没有幸运地找到这样的光泽函数,也没有尝试在键盘事件回调中调用OpenGL readPixels.看起来光泽会将图片渲染到窗口而不会暴露渲染的位图.

如果在光泽度上很难做到这一点,是否存在具有实时高级位图操作(平移,旋转,透明度)的替代方案？

Answer 1

事实证明readPixels可以用在这种情况下。我在挖掘 #haskell 聊天日志时发现了这个片段：

-- save a screenshot to a handle as binary PPM
snapshotWith :: (BS.ByteString -> IO b) -> Position -> Size -> IO b
snapshotWith f p0 vp@(Size vw vh) = do
  let fi q = fromIntegral q
      p6 = "P6\n" ++ show vw ++ " " ++ show vh ++ " 255\n"
  allocaBytes (fi (vw*vh*3)) $ \ptr -> do
    readPixels p0 vp $ PixelData RGB UnsignedByte ptr
    px <- BSI.create (fi $ vw * vh * 3) $ \d -> forM_ [0..vh-1] $ \y ->
      BSI.memcpy
        (d`plusPtr`fi(y*vw*3))
        (ptr`plusPtr`fi ((vh-1-y)*vw*3))
        (fi(vw*3))
    f $ BS.pack (map (toEnum . fromEnum) p6) `BS.append` px

writeSnapshot :: FilePath -> Position -> Size -> IO ()
writeSnapshot f = snapshotWith (BS.writeFile f)

来自https://gitorious.org/maximus/mandulia/source/58695617c322b0b37ec72f9a0bd3eed8308bf700:src/Snapshot.hs