Cannot Assign TBitmapCanvas to TBitmapCanvas

[sk.Silvia]

hi alle

ich hab probleme mit diesen part fo code

Delphi-Quellcode:

  
  procedure TEngine.Show;
  var tmp:TBitmap;
      begin
      tmp:=TBitmap.Create;
      tmp.Canvas.Assign(Screen.Canvas);

      ShowScr.Canvas.Draw(-10,-10,tmp);
      ShowScr.Canvas.LineTo(50,50);
      end;

it creates a runtime error "Cannot Assign TBitmapCanvas to TBitmapCanvas" what is nonesence..isnt it??
i just only want to save the canvas into TBitmap (and dont want to make it over Pixels[], cuz its too slow)

[Dust Signs]

You could use CopyRect or BitBlt instead. And don't forget to free the tmp bitmap

Dust Signs

[sk.Silvia]

ok i used

ShowScr.Canvas.CopyRect(ShowScr.Canvas.ClipRect,Screen.Canvas,Screen.ClientRect); thats fine, but only in the case that ShowScr is the same size (width, height) as Screen, when not i get enlarged picture

[Dust Signs]

Well, why do you work with the ShowScr's cliprect then? Your method only works if the two cliprects are exactly equal (if you don't want to have anything enlarged )

Dust Signs

[marabu]

Hi Silvia,

Zitat von sk.Silvia:

i just only want to save the canvas into TBitmap

you can do that and more when you pick up GrabImage() over there: klick

Delphi-Quellcode:

procedure TDemoForm.GrabButtonClick(Sender: TObject);
begin
  with GrabImage(GetDesktopWindow) do
  begin
    if SaveDialog.Execute then
      SaveToFile(SaveDialog.FileName);
    Free;
  end;
end;

Kind regards

marabu

[sk.Silvia]

i know, but its doing the same with ClinetRect, i try to do the following

http://www.politea.sk/mpp01.jpg

the screen canvas i only work woth (isnt displayed) and diplayed is only ShowScr which contains a part of Screen.Canvas

[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

[sk.Silvia]

thank you