JPEG vs. JPEG2000: benchmarking with dermatological images.

BACKGROUND

Despite the importance of images in the discipline and the diffusion of digital imaging devices, the issue of image compression in dermatology was discussed only in few studies, which yielded results often not comparable, and left some unanswered questions.

OBJECTIVE

To evaluate and compare the performance of the JPEG and JPEG2000 algorithms for compression of dermatological images.

METHODS

Nineteen macroscopic and fifteen videomicroscopic images of skin lesions were compressed with JPEG and JPEG2000 at 18 different compression rates, from 90% to 99.5%. Compressed images were shown, next to uncompressed versions, to three dermatologists with different experience, who judged quality and suitability for educational/scientific and diagnostic purposes. Moreover, alterations and quality were evaluated by calculation of mean 'distance' of pixel colors between compressed and original images and by peak signal-to-noise ratio, respectively.

RESULTS

JPEG2000 was qualitatively better than JPEG at all compression rates, particularly highest ones, as shown by dermatologists' ratings and objective parameters. Agreement between raters was high, but with some differences in specific cases, showing that different professional experience can influence judgement on images.

CONCLUSION

In consideration of its high qualitative performance and wide diffusion, JPEG2000 represents an optimal solution for the compression of digital dermatological images.