A US company has developed software that it claims improves the compression of JPEG images by nearly a third without harming image quality.

The firm has also proposed a new standard for displaying images.

The JPEG (Joint Photographic Experts Group) standard is a commonly used method for compressing digital images and most photographic images available on the world wide web are in this format.

Allume Systems, based in California, US, says the new version of its StuffIt compression technology can reduce JPEG files by a further 28% without loss of quality. The company says this could save storage space for those with large image collections.

Details of Allume's new algorithm have yet to be published, and the company could not be reached for comment. A statement states simply that "patent pending technology is able to replace the existing JPEG compression method with a more efficient alternative".

Researchers have previously calculated that significant improvements, perhaps as high as 30%, could be achieved by enhancing certain specific aspects of the JPEG compression method.

Benchmark images
Mike Reddy, a compression expert at the University of Glamorgan in Wales, UK, says a 28% reduction in file size would be a major improvement, but says the details of the technique need to be studied. "It seems a big claim," he told New Scientist. "Where are the test results published with standard benchmark images to let us see the improved compression?"

Reddy also raises concerns about the compatibility of the format, as well as possible licensing issues.

Data compression involves finding replicated patterns in data and encoding these patterns so that they can be represented by a smaller amount of data.

"The figure is not unbelievable," says Andrew Armstrong at Loughborough University in Leicester, UK. "However, we have to remember that images with a lot of redundancy - hi-resolution images or images with linear smooth backgrounds - will compress pretty well anyway."

Raw images
Allume Systems has also developed a file format incorporating its compression technology, called StuffIt Image Format (SIF) as an alternative to JPEG. It claims SIF beats JPEG for compressing raw (24-bit) digital images, such as those captured by a digital camera.

Allume hopes SIF could replace JPEG as the dominant method for storing image files. But for the format to be widely adopted, software used to view images, including web browsers, would need to be modified to be able to decode SIF files.

Reddy believes SIF files will only gain acceptance "if the format worked without proprietary plug-ins, or there was assurance that you would not have to pay for the ability to see these images".

Another concern is how much computing power is needed to perform the compression. "If they intend people to use this format for portable devices, the processing requirements are an issue as they not only affect time but battery life too," Armstrong says.

He also notes that a new and improved version of JPEG, called JPEG2000, could provide comparable benefits: "It is not only technically advanced, but is royalty and licence-fee free as well."

From NewScientist