Cannot Assign TBitmapCanvas to TBitmapCanvas

[marabu]

Your choice of variable names confused me. Screen is a well known VCL management object and has no canvas property. It seems you have two bitmaps - one to hold a full image and one to hold an arbitrary rect cut out of the full image. CopyRect would be my choice to accomplish this. The code for ClipButtonClick is my test code:

Delphi-Quellcode:

procedure GetViewPort(bmFull, bmPart: TBitmap; TopLeft: TPoint);
var
  r: TRect;
begin
  with bmPart do
    r := Bounds(TopLeft.X, TopLeft.Y, Width, Height);
  with bmPart.Canvas do
    CopyRect(ClipRect, bmFull.Canvas, r);
end;

procedure TDemoForm.ClipButtonClick(Sender: TObject);
var
  bmFull: TBitMap;
begin
  bmFull := GrabImage(GetDesktopWindow);
  with Image.Picture.Bitmap do
  begin
    Width := Image.Width;
    Height := Image.Height;
  end;
  GetViewPort(bmFull, Image.Picture.Bitmap, Point(100, 100));
  bmFull.Free;
end;

marabu