Browsing by Author "Hung, Chi-Mao"

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Ambient-light-adaptive image quality enhancement for full-color e-paper displays using a saturation-based tone-mapping method
(2018-03-01)
Qin, Zong
;
Chen, Yi-Wen
;
Lin, Fang-Cheng
;
Hung, Chi-Mao
;
Shieh, Han-Ping David
Full-color e-paper displays that have a small color gamut encounter image tone distortions and contour artifacts in high-saturation regions. To solve these issues, in this paper, we comprehensively measure the colorimetric responses of input image signals and demonstrate that the perceptual colorfulness in terms of chroma abnormally declines when the input saturation is beyond a certain value. Accordingly, saturation-based tone-mapping curves are developed to map the abnormal high saturation to the range that the display is able to normally render. By testing several test charts and natural images, the recoveries of the original image tones and the removals of the contour artifacts are experimentally verified. More important, by discussing how to conduct a database of tone-mapping curves for different ambient lights and utilize the database for an unknown ambient light, the proposed method is proven to be completely ambient light adaptive.
Digital halftoning method with simultaneously optimized perceptual image quality and drive current for multi-tonal electrophoretic displays
(2020-01-01)
Qin, Zong
;
Wang, Hsin-, I
;
Chen, Zi-Yu
;
Chen, Chun-Ho
;
Tien, Pei-Lin
While using digital halftoning to achieve multi-tones in al bit electrophoretic display (EPD), e.g., a three-pigment chromatic EPD, the drive current is significantly increased because of frequently reversed pixel values. Aimed at this issue, this study first establishes a model that can accurately predict the drive current from image content. Next, based on the direct binary search method, a new halftoning method is proposed by constructing a combined merit function that incorporates both the perceptual image quality and the drive current. As a result, in experiments using a 13.5 in. three-pigment EPD and several test images, compared with the well-developed error-diffusion method, the proposed method produces little image quality degradation, whereas the drive current increase with respect to the minimum current of the EPD is reduced from 71.8 to 33.0 mA, for a significant reduction of 54.0%. (C) 2019 Optical Society of America