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;