| The conventional binary image coding techniques can provide very low compression ratio on ordered-dither image, because it does not consider the property of halftoning image. Considered the different influence of the dither threshold matrix on the ordered-dither image, a preprocessor procedure for halftoning image is constructed. Based on the combine of the run-length algorithm and the Huffman algorithm, a lossless compression method of ordered-dither image is proposed. The experimental results show that the proposed methods can get higher compression rate.Lossless compression ratio obtained on the error-diffusion images are low, which lead us to investigate lossy compression. Therefor, a method of inverse halftoning is used to convert error-diffusion image back to the contone image. A lossy compression method for error-diffusion image which based on the inverse halftoning and an improved DCT coding algorithm is constructed. The experimental results indicate that the proposed algorithms adapts to the error-diffusion image, and the quality of the decode image is well. |
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