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.

A low bit rate image coding scheme which incorporates the Homomorphic property of image, Transform Coding, Vector Quantization and Human Visual System model is described. Experimental results indicate that reasonably good reconstructed images are obtained at around 0.2 to 0.25 bits per pixel dependent on the nature of the images.

algorithm for dynamic color quantization of image sequences, which quantizes each image independently to Many display devices now ada ys still allo w a limitedqroduce a different color Palette for each image. Benumber of colors, called color palette, to be displayed sides, they suggest the approach of color palette filling simultaneously. Besides, images and videos in most to prev en ffreauent switc hinrof color Dalettes. which w orld wide wb (WWW) databases are in compressed formats. Therefore, it becomes an important issue to retriev e 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 videos are presen ted. The proposed approaches use the reduced image rather than the whole image for the color palette design to avoid the heavy computation in video decompression. Experimental results show that output image qualit yof 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.