Patent Document ID: 4638369
Application ID: 06646878
Patent Status: 1

Claim One:
1. A method of producing an enhancement value for enhancing the edges of a halftone copy of a halftone original comprising the steps of: scanning the original to produce a one bit per pixel raster, isolating an m bit by m bit segment of the raster, where m is an odd number, and the N bit is the center bit, calculating an edge sharpness value of the horizontal edges directly above and below the N bit, calculating an edge sharpness value of the vertical edges directly to the left and right of the N bit, for each direction, finding a most positive and a most negative sharpness value from the two sharpness values and zero, taking the root mean square of the two most positive values, and of the two most negative values, to create positive and negative enhancement values, testing the enhancement values by dividing their difference by the larger of the two, and comparing the absolute value of the result of said division to a first threshold, using the positive enhancement value as the enhancement value if N is a "1" and the first threshold was not exceeded, using the negative of the negative enhancement value as the enhancement value if N is a "0" and the first threshold was not exceeded, using the positive enhancement value as the enhancement value if the positive value is larger than the negative value, and if the first threshold was exceeded, selecting the negative of the negative enhancement value as the enhancement value if the negative value is larger than the positive value, and if the first threshold was exceeded, testing the absolute value of the selected enhancement value against a second threshold, adding the selected enhancement value to the sum of the "1" bits in said m by m bit segment to create an edge enhanced gray scale pixel if the second threshold is exceeded, or adding nothing to said sum if the second threshold is not exceeded.