Image resizer

[DeddyH]

Here' s a procedure I wrote for a similar task. It converts a TGraphic into a TJPEGImage proportionally. For this you have to add the "jpeg"-unit to your uses-clause.

Delphi-Quellcode:

procedure StretchGraphic(const src: TGraphic;  //the TGraphic to convert
                         const dest: TJPEGImage;  //the TJPEGImage which receives the converted graphic
                         const DestWidth, DestHeight: integer); //maximum width and height of the destination jpeg
var temp, aCopy: TBitmap;
    faktor: double;
begin
  if src.Width > DestWidth then
    begin
      faktor := DestWidth / src.Width;
      if (src.Height * faktor) > DestHeight then
        faktor := DestHeight / src.Height;
    end
  else
    begin
      faktor := DestHeight / src.Height;
      if (src.Width * faktor) > DestWidth then
        faktor := DestWidth / src.Width;
    end;
  aCopy := TBitmap.Create;
  try
    aCopy.PixelFormat := pf24Bit;
    aCopy.Assign(src);
    temp := TBitmap.Create;
    try
      temp.Width := round(src.Width * faktor);
      temp.Height := round(src.Height * faktor);
      try
        SetStretchBltMode(temp.Canvas.Handle,HALFTONE);
        StretchBlt(temp.Canvas.Handle,
                   0,0,temp.Width,temp.Height,
                   aCopy.Canvas.Handle,
                   0,0,aCopy.Width,aCopy.Height,
                   SRCCOPY);
        dest.Assign(temp);
      except
        on E: Exception do
          MessageBox(0,PAnsiChar(E.Message),nil,MB_OK or MB_ICONERROR);
      end;
    finally
      temp.Free;
    end;
  finally
    aCopy.Free;
  end;
end;