휴대용 디스플레이의 적응 화질 모델
Adaptive Image Quality Model for a Mobile Display
유장진, Guihua Cui*, M. Ronnier Luo* LG 디스플레이, *University of Leeds
jjyoo2@yahoo.com
An adaptive image-quality model that incorporates the ambient illumination conditions were developed by carrying out a series of psychophysical experiments for assessing the image quality under dark, bright and outdoor bright surround conditions. Five natural scenes were rendered according to variations in lightness, chroma and hue angle (see Fig. 1). The observers assessed each of these rendered images and rated its IQD between two images in a pair viewed sequentially on the screen.
Two objective measures (colour-difference metric and colour-naturalness metric(1)) were employed to predict image quality. The colour-difference metric was considered in the CIECAM02 and CAM02-UCS(2) spaces. Two colour appearance space-based models did not
show a clear linear relationship with the visual IQ difference. It was analysed that hue-rendered images showed poor correlation and, however, lightness and chroma-rendered images showed a good linearity. With some hue-rendered images excluded, the relationship between the IQD and the colour differences shows a good linear correlation (see Fig. 2 (a)).
The colour-naturalness metric considering a human cognitive factor like memory colour was also tested. The adaptive image-quality model using the colour-appearance attributes did not perform well under two illuminated surrounds. However, the empirical adaptive image-quality
models outperformed the other models.
(a) Picnic (b)Ladies (c) Fruits (d) Skytower (e) Park
Figure 1. Five natural scenes used in the psychophysical experiments
0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
Adaptive IQD Model (CD) S ub je ct iv e IQ D 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
Adaptive Empirical IQD Model (CNM) S ub je ct iv e IQ D ● Dark ● Bright ● Outdoor bright 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
Adaptive Empirical IQD Model (CNM) S ub je ct iv e IQ D ● Dark ● Bright ● Outdoor bright
(a) Colour difference model (b)Colour naturalness model
Figure 2. Subjective IQ difference vs. Adaptive IQ difference models
References References References References
1. J. J. Yoo, G. Cui, and M. R. Luo, “Colour-naturalness Metric for Evaluating Image Quality of Mobile Displays,” Color Imaging XIV: Displaying, Hardcopy, Processing, and Applications, SPIE Vol.7241724172417241, 72410I (2009).
2. M. R. Luo, G. Cui, and C. Li, “Uniform Colour Spaces Based on CIECAM02 Colour Appearance Model,” Color Research and Application 31313131, 320 (2006).
