METHOD FOR MAINTAINING BIT DENSITY WHILE CONVERTING IMAGES IN SCALE OR RESOLUTION

A method is provided for increasing resolution of an input image in an input bitmap while performing a density preserving smoothing operation. The input bitmap includes a first set of pixels K.times.L.times.b, and the method comprises the following steps: (a) mapping the first set of pixels into a second set of individual pixels .kappa.K.times. .lambda.L.times.b, each of the individual pixels of the second set having a value selected from a set of "b" output states; (b) developing pixel arrays from the second set of individual pixels, the pixel arrays respectively representing local neighborhoods for the individual pixels of the second set, each of the local neighborhoods having a value selected from a set of "c" output states; (c) combining the output state of each individual pixel with the output state of its respective local neighborhood resulting in a selected one of a plurality of decision states, each of the decision states reflecting a current output state of a selected individual pixel and preference of the selected individual pixel for one of the selected b output states, at least one of the decision states having at least one counterpart in the set of decision states; (d) examining the individual pixels within a preselected area to locate a preselected number of individual pixels including a first individual pixel having a selected one of the decision states and at least a second individual pixel having a counterpart value to the selected one of the decision state of the first individual pixel; and (e) altering the respective output states of the first and second individual pixels when each of the first and second individual pixels are within the preselected area wherein the resolution of the output image is changed and the output image is smoothed without altering the density of the output image relative to the input image.