Re: ImageIO.write - compression

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 08 Apr 2007 12:57:27 -0700

Message-ID:

<IObSh.397089$Ju2.125924@newsfe16.lga>

Rupert Woodman wrote:

That's interesting - thanks very much for the tip.
I've done that, but changing the compression quality between the 3 allowed
values (0.5, 0.75 & 0.95) results in the same size file - is that a surprise
to you? I expected that if I changed the compression quality to 0.95, I'd
have a larger file that if I used a value of 0.05 (I got that by reading the
Java doc on ImageWriteParam)

Many thanks

Now that I look at your code more carefully, you look to be missing some
pieces. Take a look at the code below.

import java.awt.image.*;
import java.io.*;
import java.util.*;
import javax.imageio.*;
import javax.imageio.stream.*;
import javax.imageio.plugins.jpeg.*;

public class JPEGWriter {
     public static void write(RenderedImage image, float quality,
      File file) throws IOException {
         ImageWriter writer = null;
         Iterator iter = ImageIO.getImageWritersByFormatName("JPEG");
         if (!iter.hasNext())
             throw new IOException("No Writers Available");
         writer = (ImageWriter)iter.next();
         if (file.exists())
             file.delete();
         ImageOutputStream ios = ImageIO.createImageOutputStream(file);
         writer.setOutput(ios);
         JPEGImageWriteParam iwp = new JPEGImageWriteParam(null);
         iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
         iwp.setCompressionQuality(quality);
         writer.write(null,new IIOImage(image,null,null),iwp);
         ios.flush();
         writer.dispose();
         ios.close();
     }
}

--

Knute Johnson
email s/nospam/knute/