Importance

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Abstract

Edge or contour information is extracted from an image array by filtering and encoded. In order to improve reproduction accuracy, two separate filters are used to detect edge information. One of the filters detects 'sharp' edges, or edges in which the discontinuity in pixel intensity values occurs over a range of a few pixels. The other filter detects 'level' edges in which the pixel intensity value discontinuity occurs over a larger range of pixels than the 'sharp' edges. The 'smooth' areas between edges or contours are assumed to vary continuously between the contours, but for efficient implementation, a one-dimensional linear interpolation is used to regenerate the contour information between edges. In addition, to further improve performance, a line is fitted to the pixel intensity data. The end values of this line are then used for the pixel intensity data. In order to still further improve performance, the pixel intensity values associated with each contour are divided into groups and each group is then encoded. Another improvement is accomplished by mean coding the residual error.

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First Claim