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How to print bitmaps and controls placed on a TPanel (Views: 100)


Problem/Question/Abstract:

I have placed several images and assorted graphic controls on a TPanel. Now I want to print it. My problem is that the panel does not have a canvas property. Somehow I should be able to manipulate the "graphics" on the panel. What I thought might work is to do a screen capture of the panel area, but I am not sure what the function calls are. Does anybody have any ideas? I want to be able to scale the image and print it to a specific part of the page.

Answer:

The form has a canvas. You can create a new bitmap the same size as your panel and then use CopyRect to copy the panel and its content from the form to this in- memory bitmap. Then you can print the in-memory bitmap. Here's an example:

procedure TFormPrintWindows.ButtonPrintPanelClick(Sender: TObject);
var
  Bitmap: TBitmap;
  FromLeft, FromTop, PrintedWidth, PrintedHeight: Integer;
begin
  Printer.BeginDoc;
  try
    Bitmap := TBitmap.Create;
    try
      Bitmap.Width := Panel1.Width;
      Bitmap.Height := Panel1.Height;
      Bitmap.PixelFormat := pf24bit; {Avoid palettes}
      {Copy the panel area from the form into a separate bitmap}
      Bitmap.Canvas.CopyRect(Rect(0, 0, Bitmap.Width, Bitmap.Height),
                        FormPrintWindows.Canvas, Rect(Panel1.Left, Panel1.Top, Panel1.Left +
                        Panel1.Width - 1, Panel1.Top + Panel1.Height - 1));
      {Assumes 10% left, right and top margin}
      {Assumes bitmap aspect ratio > ~0.75 for portrait mode}
      PrintedWidth := MulDiv(Printer.PageWidth, 80, 100); {80%}
      PrintedHeight := MulDiv(PrintedWidth, Bitmap.Height, Bitmap.Width);
      FromLeft := MulDiv(Printer.PageWidth, 10, 100); {10%}
      FromTop := MulDiv(Printer.PageHeight, 10, 100); {10%}
      PrintBitmap(Printer.Canvas, Rect(FromLeft, FromTop, FromLeft + PrintedWidth,
        FromTop + PrintedHeight), Bitmap);
    finally
      Bitmap.Free
    end;
  finally
    Printer.EndDoc
  end;
end;

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