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Image quality reduction

apriks
apriks asked
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Last Modified: 2012-06-27
I have emade a couple of applets showing a slideshow with images.
When the images (gif or jpg) appear in the applet, the quality is
reduced from the original image. It seem like they show up in 16 colors
or non-dithered or something.
I have tried different images, but the problem appear each time.
Doesnt java support a 256 color dithered gif ??

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Commented:
When a true color (16-Million) display is not available, the majority of Java platforms convert the image into Web colors, a 256-color pallete agreed upon by all browsers.

The best answer I have to fix this problem is to convert the images to Web colors, as a gif, before you upload them.  Photoshop does an excellent job of converting the images, and 4.0 has an option under mode-indexed color to choose web colors directly.  It will look a little bit dithered by being in 256 color mode, but Photoshop's algorithm is much better.

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mgk

Commented:
You can fix the dithering problem with Netscape by creating the image again from a memory source.

Check out http://www.powerup.com.au/~mgk/java/banner.html, if you view source you will see that most of the banners are full colour GIFs. In this case I ran it all through a Filter that did nothing to the image data, but you could also convert all the data into an array and then create an image with it. Images created from memory don't dither. Here's the code:

Image tempimage=getImage(getCodeBase(),getParameter("banner"+i));
ImageFilter f=new FixDither();
ImageProducer producer=new FilteredImageSource(tempimage.getSource(),f);
image=this.createImage(producer);


class FixDither extends RGBImageFilter {
  public void FixDither() {
    canFilterIndexColorModel = true;
  }
      
  public int filterRGB(int x, int y, int rgb) {
    return rgb;
  }
}
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