Compare Image by Pixel

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;