Adaptive and Outline-Based Subsampling of Images Containing Text and Binary Graphics Lawrence O’Gorman

For digital display of scanned documents containing text and other binary graphics including line drawings, there is often the need to reduce the image size so that it can be more completely viewed on a computer monitor. We present an approach entailing two complementary methods: adaptive subsampling and outline based subsampling. The adaptively subsampling method reduces image size by preferentially removing ‘‘low-information’ ’ or ‘‘silent’ ’ rows and columns. These lowinformation regions can be located in margins, between text lines, and even through lines of graphics and text. The outline-based subsampling method entails boundary determination, polygonal fitting, smoothing of this result, and finally reduction in size of these polygonal boundaries (rather than pixels as in the conventional approach). Together, or separately, these methods yield a higher quality, subsampled image. Results of the approach are shown. The limits in terms of image reduction versus readability are discussed. 1