decompressing JPEG2000 images in java

[vinod chemmi]

Hi Experts,

I am doing compression of JPEG2000 images using jai.imageio as below codes snippets,

                 J2KImageWriteParam jwp = (J2KImageWriteParam) writer.getDefaultWriteParam();
	            
	            jwp.setLossless(lossless);
	       
	            // jwp.setFilter(J2KImageWriteParam.FILTER_97);
	            if (!lossless) {
	                  jwp.setEncodingRate(8.0 / compressionRatio);
	            }

	            ByteArrayOutputStream baos = new ByteArrayOutputStream();
	            try {
	                  ImageOutputStream ios = ImageIO.createImageOutputStream(baos);
	                  writer.setOutput(ios);
	                  writer.write(null, new IIOImage(image, null, null), jwp);
	                  ios.flush();
	                  ios.close();
	            } catch (IOException e) {
	                  e.printStackTrace();
	            }

	            byte[] jp2 = baos.toByteArray();

Any body knows , the same way how can i decompress a compressed JPEG2000 images ?

Thanks in advance.

[Rob Spoor]

You can't. JPEG is lossless. Once you compress it, there is no way of getting back the original.

[Campbell Ritchie]

By lossless, do you mean lossy, Rob? I always thought jpeg was a lossy algorithm. If you want a lossless format, don’lt you use .png?

[Rob Spoor]

You are of course very right. Lossy, not lossless. If it were lossless it would be no problem at all to decompress it.

[Winston Gutkowski]

Rob Spoor wrote:You are of course very right. Lossy, not lossless. If it were lossless it would be no problem at all to decompress it.

Actually, there are quite a lot of utilities around that can convert a JPEG image to a bitmap. Wouldn't that be considered decompressing?

I also have no idea whether the same capabilities exist in Java.

@Vinod: If you do that, you'll get whatever quality the JPEG was saved with. And it'll take up a LOT more space; so, unless you think you need it, I wouldn't bother.

Winston

[Ulf Dittmer]

These days, I wouldn't use JAI for anything. I think there's a plugin for javax.imageio.ImageIO that allows it to use Jpeg2000.

[Ulf Dittmer]

This is what I meant: http://java.net/projects/imageio-ext/

[vinod chemmi]

Ulf Dittmer wrote:This is what I meant: http://java.net/projects/imageio-ext/

@Winston & Campwel,

i am doing some Iris Biometric study with biometric service providers. My requirement is to convert some kind1 iso images to raw images. Also i got some .NET application for doing it, but couldn't find java code for doing it.
So i want JPEG itself, not png.

Thanks for reply.

[Winston Gutkowski]

vinod chemmi wrote:i am doing some Iris Biometric study with biometric service providers. My requirement is to convert some kind1 iso images to raw images.

OK, but it's the "raw image" part that I don't follow. Even at 100% quality, a JPEG image is lossy, as explained above, so conversion back to a raw image will result in some loss of detail. There are several proprietary "raw image" protocols around, mostly provided by digital camera companies for use in their own equipment, that contain a lot more information than just the bitmap of pixels, and may even involve some lossless compression.

As for 'kind1', the only pages I've been able to find on Google are for (a) a Chinese snack-food company, or (b) genetic mutation; so I'm not quite sure what either would have to do with biometrics.

I think we need a bit more detail please.

Winston