I'm tring to find a better performance JPEG Decoder using java. I've
tried ImageIO, JAI and JPEGImageDecoder. The test program is attached
below. Here are the averaged numbers that I got for reading 1128 x 1024
x 8 bit jpeg images:

ImageIO  JAI.create  JPEGImageDecoder
-------  ----------  ----------------
295 ms   631 ms      161 ms
282 ms   616 ms      169 ms
295 ms   616 ms      158 ms

Currently we use JPEGImageDecoder which is the fastest of the three but
still it takes up a lot of CPU time.

Any suggestion? Thanks in advanced.

Also, just curious why JAI reader is that much slower compared with the
other two?

=========== test code ================
import java.io.File;
import java.io.FileInputStream;

import javax.imageio.ImageIO;
import javax.media.jai.JAI;
import javax.media.jai.RenderedImageAdapter;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageDecoder;

public class JPEGReaderTester {
   long start = 0, end = 0;

   enum ImageReadType {
       IMAGEIO("ImageIO"), JAI("JAI"), JPEGDECODER("JPEGDecoder");

       private String value = null;
       private ImageReadType(String s) {
           value = s;
       }

       public String value() {
           return value;
       }
   }

   private static long readFromImageIO(String filename) throws
Exception {
       File f = new File(filename);
       long start = System.currentTimeMillis();
       BufferedImage buff = ImageIO.read(f);
       long end = System.currentTimeMillis();
       return (end - start);
   }

   private static long readFromJAI(String filename) throws Exception {
       long start = System.currentTimeMillis();
       RenderedImage img = (RenderedImage) JAI.create("fileload",
filename);

       RenderedImageAdapter ria = new RenderedImageAdapter(img);
       BufferedImage bi = ria.getAsBufferedImage();
       long end = System.currentTimeMillis();
       return (end - start);
   }

   private static long readFromJPEGDecoder(String filename) throws
Exception {
       FileInputStream in = new java.io.FileInputStream(filename);
       long start = System.currentTimeMillis();
       JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(in);
       BufferedImage jpeg = decoder.decodeAsBufferedImage();
       in.close();
       long end = System.currentTimeMillis();
       return (end - start);
   }

   private static long readImageFilesByType(ImageReadType type, String
filename) throws
         Exception {
       if (type == ImageReadType.IMAGEIO) {
           return readFromImageIO(filename);
       } else if (type == ImageReadType.JAI) {
           return readFromJAI(filename);
       } else if (type == ImageReadType.JPEGDECODER) {
           return readFromJPEGDecoder(filename);
       } else {
           return 0;
       }
   }

   private static void readImageFiles(ImageReadType type) {
       long total = 0;
       try {
           String[] files = {
                            "c:\\temp\\abc.jpg",
                            "c:\\temp\\efg.jpg"
           };

           for (int i = 0; i < files.length; i++) {
               total += readImageFilesByType(type, files[i]);
           }
           System.out.println("Average time for " + type.value() + "
takes: " +
                              total / files.length + " ms");
       } catch (Exception e) {
           e.printStackTrace();
       }
   }

   public static void main(String[] args) {
       readImageFiles(ImageReadType.IMAGEIO);
       readImageFiles(ImageReadType.JAI);
       readImageFiles(ImageReadType.JPEGDECODER);
   }
}