something I do, is to use a Java-Applet that rescales the users images
on the client side.
pros:
 * rescaling is done on the client side: so you only transfer the
smaller rescaled version
   * but if you also want thumbnails you have to compute them on the
server again
 * the applet offers convenient functions to choose/display the images
   * the user can even rotate the pics before uploading
   * or drag/drop the files from the windows-explorer to the applet
cons:
 * if java is deactivated or not present, you have to offer a plain
html upload as alternative
   * the you need the resize logic on the server anyway
 * rescaling is done on the client side: this also means that the
client has to do more work - needs memory and cpu
 * GWT-to-Applet communication is everything but easy
 * you should sign the applet to get rid of security warnings

http://jupload.sourceforge.net/applet-basic-picture.html
this is open source, so you could browse it to see how they rescale
your pic

other alternative would be to use e.g. flash


On Aug 25, 4:47 pm, Manuel Carrasco Moñino
<[email protected]> wrote:
> This is a simple example to resize and change the format of an image in the
> server side.
> I hope it helps you
>
> Manolo Carrasco
>
> import java.awt.Graphics;
> import java.awt.Image;
> import java.awt.image.BufferedImage;
> import java.io.File;
> import java.io.IOException;
>
> import javax.imageio.ImageIO;
> import javax.swing.ImageIcon;
>
> public class ImageManipulator {
>   public static void main(String[] args) throws IOException {
>     transform("image.jpg", "image.png", 100, 100, "png");
>   }
>
>   public static void transform(String fileOrig, String fileFinal, int width,
> int height, String format) throws IOException {
>
>     File file = new File(fileOrig);
>     BufferedImage buffImgOrig = ImageIO.read(file);
>
>     ImageIcon thumb = new ImageIcon(buffImgOrig.getScaledInstance(width,
> height, Image.SCALE_SMOOTH));
>     BufferedImage buffImgFinal = new BufferedImage(thumb.getIconWidth(),
> thumb.getIconHeight(), BufferedImage.TYPE_INT_RGB);
>     Graphics g = buffImgFinal.getGraphics();
>     g.drawImage(thumb.getImage(), 0, 0, null);
>
>     File outputfile = new File(fileFinal);
>     ImageIO.write(buffImgFinal, format, outputfile);
>
>   }
>
> }
>
> 2009/8/25 (श्री) GNU Yoga <[email protected]>
>
>
>
> > hi
>
> > On Aug 25, 1:22 pm, Zé Vicente <[email protected]> wrote:
> > > Hello all,
>
> > > This question is not 100% GWT oriented, but I need your help and
> > > experience regarding photo album applications.
>
> > perhaps u can try smartgwt it a gwt wrapper around smartclient js
> > libraries
>
> > Its takes a while (around 2-10 sec based on your connection) to load
> > the initial js libraries, but once loaded its quiet faster
>
> >http://www.smartclient.com/smartgwt/showcase/#featured_tile_filtering
>
> > - sree
>
>
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