Question

If I wanted to move / shift the pixels of a bitmap how could I do so?

procedure MovePixels(Bitmap: TBitmap; Horizontal, Vertical: Integer);
begin
  { move the Bitmap pixels to new position }
end;

Example:

By calling MovePixels(Image1.Picture.Bitmap, 20, 20) for example would output like so:

It would be useful to also specify / change the color of the canvas that is left showing after moving the pixels. So in this example that gray / brown color could be blue etc.

I noticed there is Bitmap.Canvas.Pixels and Bitmap.Canvas.MoveTo properties, is this what I would need to do this?

I really don’t know and I bet it is so simple..

Answer 1

You can’t easily move pixels, but you can make a copy.

var
  Source, Dest: TRect;
....
Source := Rect(0, 0, Bitmap.Width, Bitmap.Height);
Dest := Source;
Dest.Offset(X, Y);
Bitmap.Canvas.CopyRect(Dest, Bitmap.Canvas, Source);

What remains is to fill in the space with the colour of your choice which I am sure you can do easily enough with a couple of calls to FillRect.

However, I think that it would be simpler not to attempt this in-place. Instead I would create a new bitmap. Perhaps like this:

function CreateMovedImage(Bitmap: TBitmap; X, Y: Integer; BackColor: TColor): TBitmap;
var
  Source, Dest: TRect;
begin
  Source := Rect(0, 0, Bitmap.Width, Bitmap.Height);
  Dest := Source;
  Dest.Offset(X, Y);

  Result := TBitmap.Create;
  Try
    Result.SetSize(Bitmap.Width, Bitmap.Height);

    Result.Canvas.Brush.Style := bsSolid;
    Result.Canvas.Brush.Color := BackColor;
    Result.Canvas.FillRect(Source);

    Result.Canvas.CopyRect(Dest, Bitmap.Canvas, Source);
  Except
    Result.Free;
    raise;
  End;
end;