Limited color display for compressed image and video

Abstract

Abstract-Many display devices nowadays still allow a limited number of colors, called color palette, to be displayed simultaneously. Besides, images and videos in most World Wide Web databases are in compressed formats. Therefore, it becomes an important issue to retrieve a suitable color palette from compressed domain in order to have fast and faithful color reproduction for these devices. In this paper, the color-palette design methods for compressed images and videos are presented. The proposed approaches use the reduced, rather than the whole, image for the color palette design to avoid the heavy computation in image or video decompression. Also, for compressed videos, a shifting-window scheme is proposed to smooth out color variations in the change of color palette. In these methods, we extend the dependent scalar quantization algorithm of a single image to accomplish the color palette design. Experimental results show that output image quality of proposed methods is acceptable to human eyes. In addition, empirical results show that the proposed shifting-window scheme can reduce the main problem of displaying quantized image sequences, screen flicker.Index Terms-Color display, color palette, color quantization, compressed image, compressed video.

Color quantization of compressed video sequences

“…It produces no screen flicker and can handle both zooming and panning cases. Unlike the approach used in [6], the proposed approach generates a color palette which is not biased to a single frame. As compared with the approach using DC sequences, the number of the training colors involved in the palette generation is significantly reduced, which in turn reduces the complexity of the process significantly.…”

“…VQ-DCSa A single color palette is generated for a shot with the approximated DC sequence of the shot. CQ-DCKF A single color palette is generated for a shot with the approach proposed in [6].…”

“…For example, one can select a key frame from a shot and use the colors that appear in the key frame as training vectors. One can also use the so-called discrete cosine (DC) sequence of a shot or even the DC image of the key frame of a shot to generate training vectors for training purposes [5], [6]. Using key frames to generate color palettes can reduce training vectors significantly, but it does not work when the shot of interest involves zooming and panning.…”