Resizing image in Java

Try this:

ImageIcon icon = new ImageIcon(UrlToPngFile);
Image scaleImage = icon.getImage().getScaledInstance(28, 28,Image.SCALE_DEFAULT);

We're doing this to create thumbnails of images:

  BufferedImage tThumbImage = new BufferedImage( tThumbWidth, tThumbHeight, BufferedImage.TYPE_INT_RGB );
  Graphics2D tGraphics2D = tThumbImage.createGraphics(); //create a graphics object to paint to
  tGraphics2D.setBackground( Color.WHITE );
  tGraphics2D.setPaint( Color.WHITE );
  tGraphics2D.fillRect( 0, 0, tThumbWidth, tThumbHeight );
  tGraphics2D.setRenderingHint( RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR );
  tGraphics2D.drawImage( tOriginalImage, 0, 0, tThumbWidth, tThumbHeight, null ); //draw the image scaled

  ImageIO.write( tThumbImage, "JPG", tThumbnailTarget ); //write the image to a file

If you have an java.awt.Image, resizing it doesn't require any additional libraries. Just do:

Image newImage = yourImage.getScaledInstance(newWidth, newHeight, Image.SCALE_DEFAULT);

Obviously, replace newWidth and newHeight with the dimensions of the specified image.
Notice the last parameter: it tells the runtime the algorithm you want to use for resizing.

There are algorithms that produce a very precise result, however these take a large time to complete.
You can use any of the following algorithms:

• Image.SCALE_DEFAULT: Use the default image-scaling algorithm.
• Image.SCALE_FAST: Choose an image-scaling algorithm that gives higher priority to scaling speed than smoothness of the scaled image.
• Image.SCALE_SMOOTH: Choose an image-scaling algorithm that gives higher priority to image smoothness than scaling speed.
• Image.SCALE_AREA_AVERAGING: Use the Area Averaging image scaling algorithm.
• Image.SCALE_REPLICATE: Use the image scaling algorithm embodied in the ReplicateScaleFilter class.

See the Javadoc for more info.