A First Look at the
JPEG2000 Standard

[ JPG vs LWF 100% screen size ] - [ JPG vs LWF 200% screen size ] - [ LWF at different compressions ]
[ Animated comparison ] - [ Technical comparison ]

 

The interest of this comparison lies in the fact that various interests have attempted to find a new compression scheme for the internet. None has been able to impose its own standard. The JPEG2000 group was organized to create a new standard for all, to supercede the older JPG standard. The LWF (Luratech) file standard, using the new "wavelet" compression, closely resembles the upcoming JPEG2000 standard, which in fact incorporates many of Luratech's wavelet formulas. It can be safely assumed that the new standard will closely resemble what Luratech now produces. 

The screen captures below show details of an image at full screen size. The original image is an uncompressed TIF. The images used to illustrate this page are, of course, compressed too. But I have carefully limited the compression so that no additional compression artifacts are visible in this comparison.

 

TIF, JPG and LWF at 100% screen size

At left, detail of the original TIF image.
Note detail in the stonework, clean
sky effects. 		Center, the same detail in a JPG file compressed 25 times in Smartsaver. Blockiness visible in the sky, detail remains good. At right, the new LWF format. The file has been compressed 25:1 which yields a filesize like that of the JPG. Detail suffers.

 

In the images above, at real screen size, you will note that the JPG file, at 57KB, keeps noticeably better detail in the stonework but introduces noise and blockiness. The new LWF format yields, for an equal filesize, a much cleaner picture, but loses more of the fine detail. The compression ratio for both the JPG and the LWF files is exactly 24.9:1 (almost 25:1, but not quite). While the filesize is dramatically reduced, there is also a degradation of image quality. There's no getting around that for now. You win some, you lose some. It appears to be a tradeoff.

 

 

 

TIF, JPG and LWF at 200% screen size

The screen captures below show details of an image at twice normal screen size. This small degree of magnification clearly shows the differences between a good JPG compression algorithm (in ULead Smartsaver) and the new LWF compression developed by LuraTech. Both the JPG and the LWF files are compressed at a level of 25:1 compared to the original uncompressed TIF image at left. It is clear that the new compression scheme greatly reduces the formation of false color and block artifacts (see an example of JPG artifacts in the sky near the roofline and in the clouds in the center image below), but at the cost of much lost detail.

 


 

LWF at different rates of compression

The mosaic below show details of the same image at different levels of compression.
This is essentially the same detail seen in the first set of images on this page (you can refer to that set of images to see a JPG sample).
I have not included a sample of the "lossless" LWF compression, which reduces the filesize by approximately one third. I have focused on compressions and small file sizes. The details below are each approximately 140 pixels wide and 230 pixels high and are seen full size, 100%, as they would display in a browser. The numbers displayed for each image are

      • the actual filesize for each original element of the mosaic below
      • the compression setting in the Luratech software

 102 KB

19 KB

9 KB

5 KB

 2 KB

968 bytes

484 bytes

340 bytes

 

 

Comparison of JPG and LWF - Animated files

The file below is 159KB in size and shows a small detail of the larger image that will display below it. It cycles through four frames, five seconds apiece, showing JPG and LWF files on the same frame, displayed in real screen size, at four different and successive levels of compression.

 

This next image is quite large, 722KB. It cycles slowly through nine different versions of the same image: the original uncompressed TIF, then JPG and LWF at 5:1, 10:1, 20:1 and 50:1 compression ratios. Each image is clearly marked. Be aware that all of these images have had to be transformed to the GIF format for this animation. This introduces some dithering (dot patterns) to the images, but the overall effect of each compression scheme is still plain to see. If you would like the animation to be slower, please e-mail me and I will slow it to 4 or 5 seconds a frame. (Right now it displays a frame every three seconds).

A highly detailed technical comparison of various JPG compression algorithms and the new wavelet compression scheme will be posted shortly. It will be lavishly illustrated and will clearly show the strengths and weaknesses of each scheme. A link to this comparison, which was organized by Alex Karasev, will be posted here, probably by January 16 or 17, 2000.

-- page updated January 07, 2000 --
© Robert Jeantet, Le Serveur Savoie

 

You are visitor number
(more or less) to a Serveur Savoie page
since a certain amount of time.