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Proceedings Paper

Evaluation of color spaces in the sense of rate and subjective quality
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Paper Abstract

In image coding, the distribution of quantization error is uniform across the transformed domain (i.e., coding error). To minimize visually perceptible noise, the quantization step size should suit the most sensitive area in the color space used. Consequently, we can expect to improve the coding efficiency while achieving the same subjective quality by adopting a perceptually uniform color space. Currently used image coding schemes such as JPEG and MPEG, make extensive use of the YCbCr color space. However, its perceptual non-uniformity is significant. In this paper, we introduce the uniform color space 'LST', which is obtained by smoothly deforming the CIE xy chromaticity diagram with a look-up table with 333 morphing points so that every MacAdam JND (just noticeable difference) ellipse is mapped onto or close to a unit circle. Test color images that use this LST color space, as well as the CIELAB, CIELUV and YCbCr spaces, are JPEG coded. The coding algorithm itself does not need to be changed. Subjective comparisons by six subjects of the decoded images to the originals show the superiority of LST to the three other spaces; the most commonly-used YCbCr was ranked last despite its highest PSNR. No significant difference was observed between CIELUV and CIELAB.

Paper Details

Date Published: 7 May 2003
PDF: 8 pages
Proc. SPIE 5022, Image and Video Communications and Processing 2003, (7 May 2003); doi: 10.1117/12.476648
Show Author Affiliations
Seishi Takamura, NTT Cyber Space Labs. (Japan)
Yoshiyuki Yashima, NTT Cyber Space Labs. (Japan)

Published in SPIE Proceedings Vol. 5022:
Image and Video Communications and Processing 2003
Bhaskaran Vasudev; T. Russell Hsing; Andrew G. Tescher; Touradj Ebrahimi, Editor(s)

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