用ScanLine交换红/蓝字节的快速方法

Question

目前，我循环Canvas.Pixels[]属性并读取画布上的每个像素，以交换红色/蓝色字节(出于特定原因)。但是，平均每幅图片需要2秒，我需要转换的图片超过8,000张(一夜之间)。我知道我可以使用ScanLine的一种方法来更快地完成这个任务，但是我对ScanLine一无所知--它的编码水平比我所习惯的要低得多。实现这一目标的最快方法是什么？我愿意等一段时间才能完成这一切，但如果我能把这段时间切成两半或更多，那就太好了。

现在，这是我使用的程序：

procedure SwapBytes(var Bmp: TBitmap);
var
  X, Y: Integer;
  R, G, B: Byte;
  C: TColor;
begin
  for Y := 0 to Bmp.Height - 1 do begin
    for X := 0 to Bmp.Width - 1 do begin
      C:= Bmp.Canvas.Pixels[X,Y];
      R:= GetRValue(C);
      G:= GetGValue(C);
      B:= GetBValue(C);
      Bmp.Canvas.Pixels[X,Y]:= RGB(B, G, R)
    end;
  end;
end;

添加注意:最初转换超过8,000张图片是我为什么需要这个的第一步。然而，我也将使用相同的东西在我们的软件自动转换任何图像现场，视需要。所以第三方转换器不能工作，因为我不能把这个分发给客户。

Answer 1

我会尝试下面这样的方法。此版本仅适用于24位位图：

procedure SwapRedBluePixels(ABitmap: TBitmap);
var
  X: Integer;
  Y: Integer;
  Red: Byte;
  Pixel: PRGBTriple;
begin
  // check for the bit depth, it must be 24-bit if you use PRGBTriple pointer
  // for line scan; if it wouldn't the iterated line pointers would point to 
  // another place in the memory
  if ABitmap.PixelFormat <> pf24bit then
  begin
    ShowMessage('Your bitmap has color depth different from 24-bit');
    Exit;
  end;
  // iterate through the image vertically
  for Y := 0 to (ABitmap.Height - 1) do
  begin
    // access the line of pixels and get the pointer to the first pixel of 
    // that line
    Pixel := ABitmap.ScanLine[Y];
    // iterate through the scanned line pixels horizontally
    for X := 0 to (ABitmap.Width - 1) do
    begin
      // store the pixel's red channel value
      Red := Pixel.rgbtRed;
      // modify the pixel's red channel value
      Pixel.rgbtRed := Pixel.rgbtBlue;
      // modify the pixel's blue channel value
      Pixel.rgbtBlue := Red;
      // increment to get the next pixel pointer of the scanned line
      Inc(Pixel);
    end;
  end;
end;

更新2:

此版本适用于24位和32位位图：

procedure SwapRedBluePixels(ABitmap: TBitmap);
var
  X: Integer;
  Y: Integer;
  Red: Byte;
  Size: Integer;
  Pixels: PByteArray;
begin
  // check the color depth and set the size of the pixel arrangement
  case ABitmap.PixelFormat of
    pf24bit: Size := SizeOf(TRGBTriple);
    pf32bit: Size := SizeOf(TRGBQuad);
  else
    // if the image is not 24-bit or 32-bit go away
    begin
      ShowMessage('Your bitmap has unsupported color depth!');
      Exit;
    end;
  end;

  // iterate through the image vertically
  for Y := 0 to (ABitmap.Height - 1) do
  begin
    // access the line of pixels and get the pointer to the first pixel of
    // that line
    Pixels := ABitmap.ScanLine[Y];
    // iterate through the scanned line pixels horizontally
    // for 24-bit images the pixels are stored like
    // B -> G -> R -> B -> G -> R etc.
    // for 32-bit images the pixels are stored like
    // B -> G -> R -> A -> B -> G -> R -> A etc.
    // so we can simply use e.g. byte array and iterate through
    // it, if we have 24-bit image, we have to read each element,
    // if 32-bit we have to skip the alpha (reserved) channel
    for X := 0 to (ABitmap.Width - 1) do
    begin
      // store the pixel's red channel value
      Red := Pixels^[(X * Size) + 2];
      // modify the pixel's red channel value
      Pixels^[(X * Size) + 2] := Pixels^[(X * Size)];
      // modify the pixel's blue channel value
      Pixels^[(X * Size)] := Red;
    end;
  end;
end;