Abstract: A method for enhancing the contour fidelity of printed images of two or more colors is described, which includes obtaining a digital representation of the color image and finding color separations of each color. Each color separation is enhanced by a single set of inverse symmetrical templates, the set including templates in which the second template is always the inverse of the first, and the third and fourth templates are 180 degree rotations of the first two. The resulting smoothed color separations are recombined into an enhanced image without separation error.

Abstract: The contour fidelity of reproduction of images is enhanced by matching groups of pixels with templates based on a hierarchical set of patterns. This is accomplished by isolating a symmetrical window of pixels in the image including a central pixel and matching the groups of pixels in the window with hierarchical templates. Enhancement values for the central pixel are provided based on the results of the comparison. Windows are formed so that each pixel in the image is a central pixel for at least one window. The hierarchial set of patterns is developed so that each pattern in the hierarchy is a combination of an extension pattern and the pattern immediately below it in the hierarchy. This significantly reduces the hardware requirements for implementation of the technique. Templates are developed by creating horizontal, vertical, reversed and inverted permutations of each pattern in the set.