Fast Algorithm for Reducing a Bit Image by a Factor of Two in Both Dimensions
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Exploiting the fact that a binary image typically includes large white areas, by omitting calculation of output halfwords when related input halfwords are all zero, using a table lookup method to remove alternate bits in the horizontal dimension, and reducing pairs of rows in the original image to single rows in the output image, provides a very fast two-dimensional 2:1 image reduction. The fast reduction algorithm quickly reduces a binary image by a factor of two, in both the horizontal and vertical dimensions, by reducing each 2 x 2 cluster of pels (picture elements) in the image to a single pel whose value is the logical OR of the four original pels. The algorithm proposed uses a novel combination of techniques to produce code which is significantly faster than current methods. These techniques include: 1.