JPEG 2000

It can be difficult trying to learn about the current range of graphics formats: most people assume that we have enough formats to handle all our needs. On closer inspection you may find that this diversity is a result of weaknesses in each file type. Here are just some of the common graphics file problems:

Ownership: some formats are owned by a particular company and other developers may need to pay a licensing fee before the format can be used. This adds to the cost of graphics software and hardware such as digital cameras and scanners.

Artefacts: these pesky buggers appear in images that have been highly compressed. Convert a small image on the highest JPEG compression setting and you will see stray pixels and blotchy colours emerge.

Colours: in order to keep the size down, some formats, such as GIF, will limit the number of colours to just 256. Photographs in this format take on a grainy, inconsistent appearance.

Lossy: the term lossy (pronounced ‘loss-ee’) refers to the way file formats store information. TIFF files are considered non-lossy as no data is discarded when files are saved in those formats: files are simply compressed. However, both GIF and JPEG formats discard information in order to reduce file sizes — hence, they are classed as lossy.

Size: some formats provide reasonable lossless compression (TIF) but others are very bloated (BMP).

Newer file types are evolving to address many of the problems. One of the most promising is JPEG 2000 (pronounced ‘jay peg 2000’ or the more catchy version of ‘jay two kay’). However you say it, the name is a bit misleading. It suggests that there is some compatibility between the original file type and the newcomer. They share some common points, but JPEG 2000 is substantially advanced, with new compression techniques and an important ‘non-lossy’ option.

Supporting programs

At press time, only some of the newest graphics software could create and view JPEG 2000 files. Ulead’s PhotoImpact 8 and CorelDRAW 11 are two of the first mainstream graphics packages to offer support for the format. Paint Shop Pro has not had a significant update for over two years, so it is no surprise that it doesn’t support the format.

Adobe has been inexplicably unsup­p­ortive. The flagship $1500 Photoshop 7 makes no mention of the format; the boxed version of Photoshop Elements 2 has references to JPEG 2000, but includes no functionality in the program. There is now an update available from the Adobe site but you will need to access this section via the Web site link within the program. You must be a registered user to gain access.

Unlike the current JPEG and GIF formats, direct browser support for the program is currently very low, but some third-party programs can allow your browser to display the images.

Is it worthwhile?

The short answer is definitely — but there is a risk that the format may not get off the ground and in the future you may struggle to find a program that opens your files. Like any new format, it may also take a little practice to understand which settings best suit your needs.

By using a new wavelet compression technology, JPEG 2000 offers similar image quality for smaller file sizes. Alternatively, you can get improved quality for the same file size. However, the biggest advantage is the new ‘lossless’ format. You can now chose to keep all the data — just like a TIF or bitmap file. The files are significantly larger than the lossy version, but smaller than TIF. If you intend to open, edit and close a file several times over, you can use this option to maintain higher quality at a reasonable file size.

How file sizes compare

Starting with a 10MB bitmap photograph (RGB mode, 24-bit colour, pictured on this page), the file sizes of common formats are shown below. Keep in mind that it is a little subjective to determine exactly which compression setting in JPEG 2000 and JPEG are equivalent: under high compression the nature of a picture will dramatically affect the final perception of quality.

Format Size
BMP 10.0MB
TIF (no compression) 10.0MB
TIF (with LZW) 7.6MB
JPEG 2000 (no compression, lossless) 4.4MB
JPEG 2000 (no compression, lossy) 2.5MB
JPEG (no compression*) 3.0MB
JPEG (25% quality setting) 225KB
JPEG 2000 (25% quality setting) 107KB
* JPEG has no option for a lossless save.

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