Re: ImageIO.write - compression

From:
"Rupert Woodman" <NoEmail@com>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 8 Apr 2007 19:35:22 +0100
Message-ID:
<46193607$0$8739$ed2619ec@ptn-nntp-reader02.plus.net>
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

"Knute Johnson" <nospam@rabbitbrush.frazmtn.com> wrote in message
news:Yd9Sh.434084$BK1.154711@newsfe13.lga...

Rupert Woodman wrote:

Just to ellucidate a little. I originally had code such as this shown
below. Whatever I pass into the setCompressionQuality() method (i.e. any
of 0.05, 0.75, 0.95), results in a written file of 811kb, so I assumed
this code was bad. I don't see why tho.

The BufferedImage passed to this method is created with:

BufferedImage bi = ImageIO.read(new File(c.getInputFileName()));

public void myWrite(BufferedImage bi)
{
  Iterator writers = ImageIO.getImageWritersByFormatName("jpg");
  ImageWriter writer = (ImageWriter)writers.next();
  ImageWriteParam param = writer.getDefaultWriteParam();
  param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
  System.err.println("getCompressionType: " +
param.getCompressionType());

  System.err.println("1 getCompressionQuality: " +
param.getCompressionQuality());
  param.setCompressionQuality(0.05f);
  System.err.println("2 getCompressionQuality: " +
param.getCompressionQuality());

  try {
    File ff = new File("c:/development/temp/xxx.jpg");
    ImageOutputStream ios = ImageIO.createImageOutputStream(ff);
    writer.setOutput(ios);
    writer.write(bi);
  } catch (IOException e) {
    e.printStackTrace();
  }
}

Many thanks

"Rupert Woodman" <NoEmail@com> wrote in message
news:46190521$0$8736$ed2619ec@ptn-nntp-reader02.plus.net...

Hi,

I have the following code:

String inputFilename = "input.jpg";
String outputFilename = "output.jpg";

BufferedImage bi = ImageIO.read(new File(inputFilename()));
ImageIO.write(bi, "jpg", new File(outputFilename));

The original file is about 1.5 meg in size, the written file is 240kb.
What I don't understand is what changes have been made to the image
(I've not specified any), and how I can control those changes?

Thank you for any thoughts you may have.

rgds

Rupert


Rupert:

I wrote a very similar method a while back with one difference, I delete
the file if it exists. I think I did that because of the problem that you
are having. If the file exists and you write over it it doesn't get
smaller.

--

Knute Johnson
email s/nospam/knute/

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