Test Criteria and Investigation of Uniform Color Spaces to Meet the Requirements of Future Imagery
The television and cinema industry has grown very rapidly during last few years and future displays will likely be able to cover high dynamic range (HDR) and wide color gamut (WCG). A uniform color space is desired that is suitable not only for efficient
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Abstract The television and cinema industry has grown very rapidly during last few years and future displays will likely be able to cover high dynamic range (HDR) and wide color gamut (WCG). A uniform color space is desired that is suitable not only for efficient quantization but also for color volume mapping in HDR and WCG environment. A design goal for the next generation display is Rec.2020 which is the minimum requirement for future video encoding. There are a number of aspects which must be considered while developing a color space in order to meet the requirements of future imagery. Current study lists eight different criterions to test the ability of a color space to meet these requirements. After defining the testing criteria, this study investigated four different color spaces including CIELAB, CAM16-UCS, ICaCb, and recently proposed zICaCb. Results showed that zICaCb outperformed other spaces tested for most of the measures and gave similar performance for others. Keywords Color spaces
CIELAB CAM16-UCS ICaCb zICaCb
1 Introduction Many researchers have proposed different perceptually uniform color spaces for color image encoding. Such approaches target image encoding using a minimum number of code values without introducing visible quantization artifacts or loss of M. Safdar M.R. Luo (&) State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, China e-mail: [email protected] M. Safdar Department of Computer Science, COMSATS Institute of Information Technology, Sahiwal, Pakistan M.R. Luo School of Design, University of Leeds, Leeds, UK © Springer Nature Singapore Pte Ltd. 2017 P. Zhao et al. (eds.), Advanced Graphic Communications and Media Technologies, Lecture Notes in Electrical Engineering 417, DOI 10.1007/978-981-10-3530-2_1
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image details. To encode high quality images, a color space is needed which can cover high dynamic range (HDR) and wide color gamut (WCG), and should at least meet requirements of Rec.2020 [1, 2]. The selected color space should be suitable for color image processing such as blending, fading, chroma sub-sampling, and resizing quickly, and with minimal error. It is desirable to transmit video signals in an encoding color space that is not only suitable for efficient image encoding but also for tone and gamut mapping often referred to as color volume mapping. As the volume of color essence increases, color transformations become more costly. This paper defines comprehensive testing criteria for a color space to meet the requirements of future imagery and offers minimal computational cost. Current study considered four perceptually uniform color spaces including CIELAB, CAM16-UCS (a revision of CAM02-UCS) [3, 4], ICaCb [5], and zICaCb [6]. All these color spaces are based on device independent CIE XYZ tristimulus space. The CIELAB is a CIE recommended uniform color space and CAM16-UCS is uniform color space based on CAM16 color appearance model (a revision of CIECAM02 with similar performance) [3, 4]. The CIELAB an
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