The magazine of the Melbourne PC User Group
JPEG2000 Image Format
 George Skarbek
gskarbek@melbpc.org.au


George Skarbek writes about his experiments with JPEG2000 — the latest in space-efficient formats

Image formats evolved rapidly during the early days of computing but in the last few years there have been virtually no new formats apart from JPEG2000. JPEG stands for Joint Photographic Experts Group. This new format, formalised in December 2000 is a new image coding system that uses compression techniques based on wavelet technology.

Many current image formats can produce lossless compression, that is, no information is discarded during conversion but the files sizes can be quite large. BMP and TIFF in particular can be huge while JPEG and some others are smaller. The current JPEG format reduces the file size by discarding data that the human eye cannot see and obtains an effective reduction is file size. But when the image is compressed too much, then the quality deteriorates very rapidly.

This new format can produce lossless compression as well as the lossy compression used by the existing JPEG format but the JPEG2000 image quality (in a .JP2 file) is significantly better than .JPG for the same file size, resulting in a saving of disk space without noticeable degradation of image quality.

Using the lossless option, the resulting file size is significantly smaller than a compressed TIF file.

Unfortunately this format has been very slow to gain acceptance because its creators have intended to obtain royalty fees from all sales.

In any discussion about images, a photo is worth more than a thousand words and there may be some loss of quality in the printing of these images. Using the Internet you can look at http://www.eetimes.com/story/OEG19991228S0028 to see a sample where a 3 MB image has been reduced to 19 KB as a .JP2 file and looks almost as good as the original while the 19 KB .JPG file is a very poor representation.

Another site, http://www.aware.com/products/compression/jpeg2000.html provides further comparisons and gives more background information.
 



Figure 2. One small section, shown enlarged.

 

Figure 1 at left. The entire page from
the album. This file is 16.2 MB when
saved as TIFF.

The images included with this article are from my father's family album which I scanned at a high resolution (600 dpi) to enable individual images to be blown up without loss of detail. Figure 1 represents an entire page and the TIFF file size is 16.2 MB. Saving this file as a lossless .JP2 image reduced the file size to 8.8 MB.
At medium levels of compression there is no perceptible difference when comparing JPEG and JPEG2000 formats but the image size is noticeably reduced. At 70% compression the JPEG file of the whole page is down to about 1 MB, down from 16.2, and the difference between it and the original is barely noticeable. Further reduction degrades the image.

The other images used here to illustrate the quality vs compression ratio represent less than 3% of the original image as shown at a larger size in Figure 2.

Figure 3 shows a JPEG image of Figure 2 at 97% compression which has reduced the file size to 90 KB, but making it virtually unusable. Compressing Figure 2 down to that same 90 KB file size using JPG2000 is shown in Figure 4. The quality is lower when compared with the original (Figure 2), but it's a usable image, remembering that this is less than 3% of the original photo.

Figure 5 shows the options available with JPEG2000.
 



Figure 3. The extracted portion compressed by 97% in regular JPEG format.
 



Figure 4. The same extracted
portion compressed with
JPEG2000 to the “file size”
of the Figure 3 image.
 

Figure 5 at right. Options available when saving with JPEG2000.

The price varies depending from where it is downloaded. The lowest I have seen is a US$49 plugin for Photoshop and since this article was written, version 8 of PaintShop Pro has been released with support for JPEG2000.

IrfanView needs its own plugin.

When installing the JPEG2000 plugin I did not fully read the license agreement and I am not sure if this is valid for one application or on one computer. Copying these to another computer's Plugin folder failed, stating that the product is not licensed. Most of the images for this article were done in PaintShop Pro.

Experimenting with the 56 MB file size I experienced a few problems and the program hung. With the 2 MB file there were no problems. The tests were performed on a 2.4 GHz computer with 512 MB RAM and running Windows XP.

Summary

Those who would like to store large numbers of images, or need to fit them onto a CD-ROM without loss of quality should consider JPEG2000. The main problem would appear to be in the distribution as the recipient of the images must also have this program (or the appropriate Plugin) installed. Currently I am not aware of any free JPEG2000 viewers.

Reprinted from the June 2003 issue of PC Update, the magazine of Melbourne PC User Group, Australia

[ About Melbourne PC User Group ]