Staying in the Lines
At the core of the JPEG2000 structure is a new wavelet-based compression methodology. DIG defines wavelets as "mathematical expressions that encode the image in a continuous stream, thereby avoiding the tendency toward visible artifacts that can sometimes result … from the division of an image into discrete compression blocks."
JPEG2000's wavelet technology, in contrast, is designed to provide as much as a 20 percent improvement in compression efficiency.
In addition, the new specification will also be designed to handle up to 256 channels of information. According to official DIG reports, "JPEG 2000 will be capable of describing complete alternate color models, such as CMYK, within a single file format. JPEG2000 can work seamlessly within color-managed environments, because it has the capacity to include full ICC profile information within each image file."
Another benefit of the format is the ability to access an encoded image without having to download, decode or even print the entire image file.
According to DIG, this allows for an image file to be customized concurrently with how the information will be eventually be accessed. DIG cites the following active bandwidth conservation example:
When a user clicks on a JPEG2000 image that has been set up for progressive-by-resolution access, the user will be able to see a low-res version as soon as it downloads and can then immediately decide whether or not to wait for higher resolution.
McGowan affirms that not only is progressive access a major benefit of the format, but that in delivering resolution on-demand from a single file, "JPEG2000 can be stored in resolution order," whereas JPEG is stored in blocks.
For the Web, this means revamped storage. DIG reports, "With the format, Web designers only have to store and link to a single image file for each product, which contains all of the resolution levels and detail required by any user. …Throughout the process, the users are always getting exactly the amount of resolution and detail that they require."