本文整理自网络，侵删。
uses
Vcl.Imaging.pngimage, Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,
Vcl.ExtCtrls, Vcl.ComCtrls;
procedure TForm1.btn_erzhihuaClick(Sender: TObject);
var
p: PByteArray;
Gray, x, y: Integer;
Bmp: TBitmap;
begin
Bmp := TBitmap.Create;
Bmp.Assign(img1.Picture.Bitmap);
//设置为24位真彩色
Bmp.PixelFormat := pf24Bit;
randomize;
for y := 0 to Bmp.Height - 1 do
begin
p := Bmp.scanline[y];
for x := 0 to Bmp.Width - 1 do
begin
//一个象素点三个字节
Gray := Round(p[x * 3 + 2] * 0.3 + p[x * 3 + 1] * 0.59 + p[x * 3] * 0.11);
if Gray > 120 then //全局阀值128
begin
p[x * 3] := 255;
p[x * 3 + 1] := 255;
p[x * 3 + 2] := 255;
end
else
begin
p[x * 3] := 0;
p[x * 3 + 1] := 0;
p[x * 3 + 2] := 0;
end;
end;
end;
ClearPicNoise(Bmp, 2);
img2.Picture.Bitmap.Assign(Bmp);
Bmp.Free;
end;
来源：http://www.coder163.com/language/delphi/
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