June 27, 2017 ICC-CMRF (2016-2017) An Efficient Uniform Color Space for High Dynamic Range and Wide Gamut Imagery Presenter: Muhammad Safdar (PhD) Supervisor: Prof. M. Ronnier Luo Zhejiang University, China 1 Uniform Color Space Predicts perceptual color difference No inter-dependence b/w lightness, chroma, and hue ELCH ()()() 2 2 2 Lightness Hue • K. A. G. Smet et al., LEUKOS, 2016 • I. Lissner et al., IEEE Trans. Image Process., 2012 2 Criteria for a New UCS 1 Uniformity (Local & Global) 2 Hue Linearity 3 Grey-scale Convergence Lightness Chroma 4 To uniformly encode high dynamic range signals e.g., 0-10,000 cd/m2 5 To uniformly encode wide gamut image signals e.g., Rec.2020 3 Test Spaces 1) CIELAB CIE/ISO standard 2) CAM16-UCS Accurately predicts small color difference data 3) ICTCP Dolby’s proposal for HDR and WCG 4) Jzazbz Current Proposal • CIE, Colorimetry, 2004 • C. Li et al., Color Imaging Conf., 2016 • Dolby, 2016 4 Criteria and Visual Data No. Criteria Data sets Purpose 1 Perceptual Color i) COMBVD i) Training Difference ii) OSA ii) Testing 2 Perceptual Uniformity i) COMBVD Ellipses i) Reference ii) MacAdam Ellipses ii) Testing iii) Munsell Data iii) Testing 3 Hue Linearity i) Hung & Berns i) Reference ii) Ebner & Fairchild ii) Testing iii) Xiao et al. iii) Testing 4 Wide-range Lightness i) RIT SL1 i) Testing Prediction ii) RIT SL2 ii) Training 5 Grey-scale Chroma-ratio metric (%) 3C Chroma-Ratio 100 w convergence CCCr g b • D. L. A. MacAdam, JOSA, 1942 • D. L. A. MacAdam, JOSA, 1974 • M. D. Fairchild, Electronic Imaging, 2011 5 Proposed Jzazbz space X ' bX ( b 1) Z D65 D65 D65 ' (1) YD65 gYD65 ( g 1) X D65 LX 0.41478972 0.579999 0.0146480 D65 MY -0.2015100 1.120649 0.0531008 D65 (2) SZ -0.0166008 0.264800 0.6684799 D65 n p LMS,, 14 cc12 wheren 2610 / 2 10,000 ''' 5 (3) LMS,,, n p 1.7 2523 / 2 LMS,, 1 c 3 10,000 IL 0.5 0.5 0 ' aM 3.524000 -4.066708 0.542708 ' (4) z ' bSz 0.199076 1.096799 -1.295875 1 dI z (5) J z whered 0.56 1 dI z 6 Results (Uniformity) CIELAB CAM16-UCS 100 40 30 50 20 10 M b* b 0 0 -10 -20 -50 -30 -40 -50 0 50 100 -40 -20 0 20 40 a a* M IC C J a b T P z z z 0.15 0.2 0.1 0.1 0.05 T z b -C 0 0 -0.1 -0.05 -0.2 -0.1 -0.2 -0.1 0 0.1 0.2 -0.1 -0.05 0 0.05 0.1 0.15 C a P z 7 Results (Uniformity in WCG) ICTCP Jzazbz -CT bz az CP (a) (b) 8 Results (Quantitative) 80 70 60 50 CIELABCIELAB 40 CAM16-UCSCAM16-UCS 30 ICTCPICTCP JzazbzJzazbz 20 10 0 COMBVD OSA COMBVD COMBVD MacAdam MacAdam Local Global Local Global 9 Results (Hue Linearity) 10 Results (Quantitative) 14 12 10 8 CIELABCIELAB CAM16-UCSCAM16-UCS 6 ICTCPICTCP 4 JzazbzJzazbz 2 0 Hung & Berns Hung & Berns Ebner & Fairchild Xiao et al. (blue) 11 Results (Lightness Prediction) 12 Results (Lightness) 35 30 25 20 CIELABCIELAB CAM16-UCSCAM16-UCS 15 ICTCPICTCP 10 JzazbzJzazbz 5 0 RIT SL1 RIT SL2 Munsell Value Chroma Ratio (%) 13 Conclusions Jzazbz Second best for small color difference Best for large color difference Best for wide gamut uniformity Best for hue linearity Best for wide-range lightness prediction Plausible grey-scale convergence Jzazbz gave overall best performance and should be confidently used 14 Demonstration (Image Segmentation) Segmentation (7 regions) using K-means clustering algorithm Original CIELAB CAM16-UCS YCbCr ICTCP Jzazbz Deliverables 1. Journal Paper: Optics Express (IF=3.3) https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-13-15131 2. MATLAB Code for Jzazbz 15 Any Questions? Model Development Initially, we start using a structure similar to ICTCP LX 1,1 1,21 1,1 1,2 D65 MY 1 (1) 2,1 2,2 2,1 2,2 D65 SZ 3,1 3,21 3,1 3,2 D65 n p LMS,, cc12 ''' 10,000 LMS,,, n (2) LMS,, 1 c 3 10,000 ' IL1,1 1,21 1,1 1,2 aM 1 ' z 2,1 2,2 2,1 2,2 (3) ' bSz 3,1 3,21 3,1 3,2 • Dolby, 20016 • M. Safdar et al., Color Imaging Conf., 20016 Model Development Then we introduced a linear given below to correct hue linearity ' X D65 bXD65 ( b 1) Z D65 ' (1) YD65 gYD65 ( g 1) X D65 ' LX1,1 1,21 1,1 1,2 D65 MY 1 ' (2) 2,1 2,2 2,1 2,2 D65 SZ3,1 3,21 3,1 3,2 D65 n p LMS,, cc12 ''' 10,000 LMS,,, n (3) LMS,, 1 c 3 10,000 ' ILz 1,1 1,21 1,1 1,2 aM 1 ' z 2,1 2,2 2,1 2,2 (4) ' bSz 3,1 3,21 3,1 3,2 • G. Kuehni., Col. Res. Appl., 1999 • G. Cui et al., Col. Res. Appl., 2002 Model Development Another simple equation to tune perceptual lightness 1 dI z J z (5) 1 dI z after Eq.5 • M. R. Luo et al., Col. Res. Appl., 2006 .