Saving a form's image as jpg file

Yesterday, when writing about a new feature in the Blog Manager program, I wrote¹ "I thought that it would be helpful if I could save the graph as an image". I found some old tech tips that helped me write the code; some of this was very low level with reference to device contexts and similar.

Still reading "Smarter than you think"², where Clive ponders AI and Jeopardy, I got the idea of asking AI program co-pilot to write a program in Delphi to save a form's image as jpg. Well, it did, and the procedure is remarkably similar to what I pieced together, although without all the low level device contexts.

procedure TForm1.SaveFormAsJPG(const FileName: string);
var
  Bitmap: TBitmap;
  JpegImage: TJpegImage;
  
begin
  Bitmap:= TBitmap.Create;
  JpegImage:= TJpegImage.Create;
  try
    // Capture the form's image
    Bitmap.Width:= Self.ClientWidth;
    Bitmap.Height:= Self.ClientHeight;
    Self.PaintTo (Bitmap.Canvas.Handle, 0, 0);

    // Convert the bitmap to JPG
    JpegImage.Assign(Bitmap);

    // Save the JPG to a file
    JpegImage.SaveToFile(FileName);
  finally
    Bitmap.Free;
    JpegImage.Free;
  end;
end;

I don't want the entire form to be saved, only the graph, so it may be that the critical PaintTo procedure will not be available for a TChart that is apparently based on TPanel. I'll have to check this*. As far as I can see, the PaintTo procedure hides all the device context code.

* Indeed, CoPilot's code works, even when 'self' is replaced by 'chart1'. Well done!

Internal links
[1] 1874
[2] 1873

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