Name: ddT132432 Date: 01/10/2002


FULL PRODUCT VERSION :
java version "1.4.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta3-b84)
Java HotSpot(TM) Client VM (build 1.4.0-beta3-b84, mixed mode)

FULL OPERATING SYSTEM VERSION :
Microsoft Windows 2000 [Version 5.00.2195]

A DESCRIPTION OF THE PROBLEM :
There is a bug in the
com.sun.imageio.plugins.jpeg.JPEGImageWriter.write().
In the lines

            switch(param.getCompressionMode()) {
            case ImageWriteParam.MODE_DISABLED:
                throw new IIOException("JPEG compression cannot be disabled");
            case ImageWriteParam.MODE_EXPLICIT:
                float quality = param.getCompressionQuality();
                qTables = new JPEGQTable[2];
>>>>> qTables[0] =JPEGQTable.K1Div2Luminance.getScaledInstance(quality, true);
                qTables[1] =JPEGQTable.K2Div2Chrominance.getScaledInstance(quality, true);
                break;

there is a call to
JPEGQTable.K1Div2Luminance.getScaledInstance(quality, true);

This method requires a quality value from 1 to 255.
Unfortunately, quality is a value between 0 and 1.
This restriction is enforced by
javax.imageio.ImageWriteParam.setCompressionQuality().

This means you can't compress jpeg images!

The fix is to either modify
com.sun.imageio.plugins.jpeg.JPEGImageWriter.write().
or
JPEGQTable.K1Div2Luminance.getScaledInstance()

to translate the quality to some value between 1 and 255.

Here is a test program if you need to test it out.
Run the program with

    java bug1 <input-jpg-file> <output-jpg-file>
<compression-factor>



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. run the supplied test program with compression values
from 0 to 1 using a jpeg image that's at least 50K in size.
you will not be able to compress it very much.
e.g. compression to 10K is impossible.

EXPECTED VERSUS ACTUAL BEHAVIOR :
using a compression value of .05 should result
in a very small-sized image file.

using a compression value of 1.0 should result
in a very large-sized image file.

This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.imageio.*;
import javax.imageio.stream.*;

public class bug1 {
    public static void main(String[] args) {
        // Create a image to save

        // Write generated image to a file
        try {
//
            RenderedImage rendImage = ImageIO.read(new File(args[0]));

            File file = new File(args[1]);
            file.delete();
            ImageOutputStream ios = ImageIO.createImageOutputStream(file);
    
            ImageWriter writer = null;
            Iterator iter = ImageIO.getImageWritersByFormatName("jpg");
            if (iter.hasNext()) {
                writer = (ImageWriter)iter.next();
            }

            writer.setOutput(ios);
            ImageWriteParam iwparam = writer.getDefaultWriteParam();
            iwparam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT) ;
            System.out.println(iwparam.getCompressionQuality()) ;
            iwparam.setCompressionQuality(Float.parseFloat(args[2])) ;
            writer.write(null, new IIOImage(rendImage, null, null), iwparam);
            ios.flush();
            writer.dispose();
            ios.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

---------- END SOURCE ----------
(Review ID: 137909)
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