Color image compression using quantization, thresholding, and edge detection techniques all based on the moment-preserving principle

  • Authors:
  • Chen-Kuei Yang;Wen-Hsiang Tsai

  • Affiliations:
  • Department of Information Management, Ming Chuan University, 250, Sec. 5, Chung Shan N. Rd., Shih-Lin, Taipei 111, Taiwan, ROC;Department of Computer and Information Science, National Chiao Tung University, HsinChu 300, Taiwan, ROC

  • Venue:
  • Pattern Recognition Letters
  • Year:
  • 1998

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Abstract

A new approach to color image compression with high compression ratios and good quality of reconstructed images using quantization, thresholding, and edge detection all based on the moment-preserving principle is proposed. An input image with 24 bits per pixel is quantized into 8 bits per pixel using a new color quantization method based on the moment-preserving principle. The quantized image is then divided into n x n non-overlapping square blocks. Two representative colors for each block are computed by moment-preserving thresholding. A bit-map is then generated, consisting of 0s and 1s indicating whether the block pixels are assigned to the first color or the second according to the Euclidean distance measure. A moment-based edge detector is performed further on the bit-map of each non-uniform block. The two parameters l and @q of a line edge with the equation of x cos @q + y sin @q = l are obtained. The image is finally coded with a codebook of a 256-color palette; a 1-bit indicator for each block which specifies whether the block is uniform or not; an 8-bit color index for a uniform block, or two 8-bit color indices, a 3-bit index for @q, and a 2-bit or 3-bit index for l for a non-uniform block. An average compression ratio of 22.49 or 33.32 can be obtained for 4 x 4 or 5 x 5 image blocks, respectively. Experimental results show the feasibility and efficiency of the proposed approach for color image compression.