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Date: Sat, 21 Sep 2002 12:03:57 +1000
From: Charles Hacker <reply.to@borland.newsgroups>
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Subject: Re: JPEG... changing size !?!?
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"Arquétipo" wrote:
> 
>    Does anyone knows how to change the size of JPEG images from 800x600 to
> 1014x618 using Delphi ?

Here is some code I use.  However it does NOT give a 'smooth' resize of
the image, (thus the resized image is not as good).
As stated in the other posting, better to use the Bitmap Resampler code.

uses jpeg;

var Jpg : TJPEGImage;
    Bmp : TBitmap;

procedure ResizeBMP(b : TBitmap; NewWidth, NewHeight : integer);
var
  tbmp : TBitmap;
begin
  tbmp := TBitmap.Create;
  tbmp.Width := b.Width;
  tbmp.Height := b.Height;
  BitBlt(tbmp.Canvas.Handle,0,0,tbmp.Width,tbmp.Height,
         b.Canvas.Handle,0,0,SRCCOPY);
  b.Width := NewWidth;
  b.Height := NewHeight;
  StretchBlt(b.Canvas.Handle,0,0,b.Width,b.Height,tbmp.Canvas.Handle,
             0,0,tbmp.Width,tbmp.Height,SRCCOPY);
  tbmp.Free;
end;

begin
  Jpg := TJPEGImage.Create;
  Bmp := TBitmap.Create;
  Jpg.LoadFromFile('FileName.jpg');
  // Copy JPEG to bitmap:
  Bmp.Width := Jpg.Width;
  Bmp.Height := Jpg.Height;
  Bmp.Canvas.Draw(0,0,Jpg);
  // Resize Bitmap
  ResizeBMP(Bmp,[newsizeW],[newsizeh]);
  // Copy BMP back to JPG
  Jpg.Assign(Bmp);
  Jpg.Free;
  Bmp.Free;
end;



-- 
Charles Hacker
Lecturer in Electronics and Computing
School of Engineering
Griffith University - Gold Coast
Australia