Попиксельное сравнение картинок

procedure
 TForm1.Button1Click(Sender: TObject);
 var

   b1, b2: TBitmap;
   c1, c2: PByte;
   x, y, i,
   different: Integer; // Counter for different pixels 
begin

   b1 := Image1.Picture.Bitmap;
   b2 := Image2.Picture.Bitmap;
   Assert(b1.PixelFormat = b2.PixelFormat); // they have to be equal 
  different := 0;
   for
 y := 0 to
 b1.Height - 1 do

   begin

     c1 := b1.Scanline[y];
     c2 := b2.Scanline[y];
     for
 x := 0 to
 b1.Width - 1 do

       for
 i := 0 to
 BytesPerPixel - 1 do
 // 1, to 4, dep. on pixelformat 
      begin

         Inc(different, Integer(c1^ <> c2^));
         Inc(c1);
         Inc(c2);
       end
;
   end
;
 end
;

Другое по теме:

• Bitmap без формы
• Bitmap.Scanline для PixelFormat
• Вращать Bitmap вокруг точки