如何转换位图使用GDI通过像素强度为灰度？

问题描述

我在寻找如何将32位位图转换使用GDI（而不是GDI +）灰度简单的解决方案。是否有例如可能通过更改位图的调色板什么？

I'm looking for the simple solution of how to convert the 32-bit bitmap to grayscale using GDI (not GDI+). Is there a possibility e.g. by changing the bitmap's pallete or something ?

当然还有很多像在Delphi例子，但我正在寻找一个WinAPI的功能，将通过线做到不反复。

Of course there is plenty of examples in Delphi like this one, but I'm looking for a WinAPI function which would do this without iteration through the lines.

推荐答案

我还没有发现任何单一的GDI函数这样做。最简单的方法，如大卫在他的评论中提到的，就是扫描每一行，并计算像素颜色。你所寻找的可能是，看到的部分2.5.1。正如我在什么地方找到这个公式例如使用即使是由著名的Adobe Photoshop。下面code例如支持，预计只有24位像素格式的位图作为输入：

There are few variations of this formula and in the following example I've used the one recommended by the ITU, see this document section 2.5.1. As I found somewhere, this formula is used e.g. even by well known Adobe Photoshop. The following code example supports and expects only 24-bit pixel format bitmaps as an input:

procedure BitmapGrayscale(ABitmap: TBitmap);
type
  PPixelRec = ^TPixelRec;
  TPixelRec = packed record
    B: Byte;
    G: Byte;
    R: Byte;
  end;
var
  X: Integer;
  Y: Integer;
  Gray: Byte;
  Pixel: PPixelRec;
begin
  for Y := 0 to ABitmap.Height - 1 do
  begin
    Pixel := ABitmap.ScanLine[Y];
    for X := 0 to ABitmap.Width - 1 do
    begin
      Gray := Round((0.299 * Pixel.R) + (0.587 * Pixel.G) + (0.114 * Pixel.B));
      Pixel.R := Gray;
      Pixel.G := Gray;
      Pixel.B := Gray;
      Inc(Pixel);
    end;
  end;
end;

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