Hi All.
I have a JPEG image, which if I convert to bitmap, then back to JPEG again, it
is not the same. The problem occurs in the stretchdraw function.
Can anyone advise how I can replicate exactly the JPEG original without copying
the JPEG original to another JPEG?
What happens is most graphics programs can load the new image, but there is a
difference I cannot ascertain which stuffs up some other graphics programs.
Thanks,
al+
procedure TForm1.btnWriteClick(Sender: TObject);
var Orig,Smaller:tjpegimage;
buffer:tbitmap;
smallFname:string;
begin
smallFname := copy(ImgData.Filename,1,length(ImgData.Filename)-4)
+'_smaller.jpg';
JpegOut.FileName := smallFName;
if not JpegOut.Execute then
exit;
SmallFName := JPegOut.FileName;
Buffer := tbitmap.Create;
Orig := tjpegImage.Create;
Smaller := tjpegimage.create;
try
Orig.LoadFromFile(ImgData.Filename);
Orig.DIBNeeded;
Buffer.PixelFormat := pf24bit;
Buffer.Width := orig.Width div 2;
Buffer.Height := orig.Height div 2;
// Even if the width & height are the same the following does not return a
//copy of the original JPEG (disregard compression etc)
Buffer.Canvas.stretchdraw(rect(0,0,Buffer.width,buffer.height),Orig);
Smaller.PixelFormat:=orig.PixelFormat;
Smaller.Assign(Buffer);
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