Seitenverhältnis von PNG-Grafiken ändern

[Uwe Raabe]

Delphi-Quellcode:

var
  hdr: TChunkIHDR;
  origin: TPoint;
  png1: TPngImage;
  png2: TPngImage;
  frame: TRect;
  size: Integer;
begin
  png1 := TPngImage.Create;
  try
    png1.LoadFromFile('c:\Temp\bild_original.png');
    size := Max(png1.Width, png1.Height);
    origin := Point((size - png1.Width) div 2, (size - png1.Height) div 2);
    frame := TRect.Create(origin, png1.Width, png1.Height);
    hdr := png1.Header;
    png2 := TPngImage.CreateBlank(hdr.ColorType, hdr.BitDepth, size, size);
    try
      png2.Canvas.Brush.Color := clWhite;
      png2.Canvas.FillRect(TRect.Create(0, 0, size, size));
      png2.Canvas.Brush.Style := bsClear;
      png1.Draw(png2.Canvas, frame);
      png2.SaveToFile('c:\Temp\bild_neu.png');
    finally
      png2.Free;
    end;
  finally
    png1.Free;
  end;
end;