I need to resize images upon upload in Java / Struts. How to do this? [closed]

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Closed 2 years ago.

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We're building an application that handles image uploads. I want users to be able to upload an image at a given size, say 128x128, and then have the server automatically generate other sizes based on that, such as 64x64, 57x57, and 25x25.

Are there libraries that can help me with this?

Edit: I should note that the resizing should take place only on upload. When the new image sizes are rendered in the browser, it should be pulling from cached copies --- not doing the resizing again. In other words, the different sizes should be generated only once, not each time the images are requested.

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From a related source in the Swing tutorial:

/**
 * Resizes an image using a Graphics2D object backed by a BufferedImage.
 * @param srcImg - source image to scale
 * @param w - desired width
 * @param h - desired height
 * @return - the new resized image
 */
private Image getScaledImage(Image srcImg, int w, int h){
    BufferedImage resizedImg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2 = resizedImg.createGraphics();
    g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g2.drawImage(srcImg, 0, 0, w, h, null);
    g2.dispose();
    return resizedImg;
}

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Utility function from from one of our java portal page (coded from example from several forum, I do not claim to be the author)

Hope this help
Guillaume PATRY

/**
 * Convenience method that returns a scaled instance of the
 * provided {@code BufferedImage}.
 *
 * @param img the original image to be scaled
 * @param targetWidth the desired width of the scaled instance,
 *    in pixels
 * @param targetHeight the desired height of the scaled instance,
 *    in pixels
 * @param hint one of the rendering hints that corresponds to
 *    {@code RenderingHints.KEY_INTERPOLATION} (e.g.
 *    {@code RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR},
 *    {@code RenderingHints.VALUE_INTERPOLATION_BILINEAR},
 *    {@code RenderingHints.VALUE_INTERPOLATION_BICUBIC})
 * @param higherQuality if true, this method will use a multi-step
 *    scaling technique that provides higher quality than the usual
 *    one-step technique (only useful in downscaling cases, where
 *    {@code targetWidth} or {@code targetHeight} is
 *    smaller than the original dimensions, and generally only when
 *    the {@code BILINEAR} hint is specified)
 * @return a scaled version of the original {@code BufferedImage}
 */
 public BufferedImage getScaledInstance(
            BufferedImage img,
            int targetWidth,
            int targetHeight,
            Object hint,
            boolean higherQuality) {
BufferedImage ret = (BufferedImage) img;
int w, h;
if (higherQuality) {
    // Use multi-step technique: start with original size, then
    // scale down in multiple passes with drawImage()
    // until the target size is reached
    w = img.getWidth();
    h = img.getHeight();
} else {  
    // Use one-step technique: scale directly from original
    // size to target size with a single drawImage() call
    w = targetWidth;
    h = targetHeight;
}

do {
   if (higherQuality) {
      if (w > targetWidth) {
         w /= 2;
         if (w < targetWidth) {
            w = targetWidth;
         }
      } else {
         w = targetWidth;
      }
      if (h > targetHeight) {
         h /= 2;
         if (h < targetHeight) {
        h = targetHeight;
         }
      } else {
         h = targetHeight;
      }
   }
   BufferedImage tmp = null;
   if (img.getType() == 0) {
      tmp = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
   } else {
      tmp = new BufferedImage(w, h, img.getType());
   }
   Graphics2D g2 = tmp.createGraphics();
   g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
   g2.drawImage(ret, 0, 0, w, h, null);
   g2.dispose();
   ret = tmp;
} while (w != targetWidth || h != targetHeight);
return ret;

}