Abstract
This paper reports a study on compression achieved on document images with different image formats, including PNG, GIF, PBM zipped, JBIG and JBIG2. It also examines the issue of perceptual quality of the bi-level document images in these formats. It analyzes the impact of a common pre-processing step, namely the adaptive thresholding, on compression ratio and perceptual image quality in different image formats. We conclude that adaptive thresholding improves the compression ratio for common image formats, like the PNG and GIF, and make them comparable to JBIG/JBIG2 encoding; they result in significant improvement in perceptual image quality also. We also observe that the simple pre-processing step prevents perceptual information-loss in JBIG/JBIG2 encoding in certain situations.
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