METHOD AND APPARATUS FOR DIGITIZING AN IMAGE
An improved method and apparatus for digitizing scanned images are disclosed. A matrix or window of pixels is centered on each pixel of the image. For each pixel, prescribed number of brightness vector differences, represented as algebraic signs, is calculated in parallel from the center pixel to surrounding pixels in the matrix. At the same time, the difference signs of the inverse vector differences between surrounding pixels and the center pixel are also calculated. Both sets of vector differences are stored and will be utilized in the vector difference sign determinations for subsequent windows. Only the difference signs (+ or -) associated with each vector and inverse vector are actually determined and stored in memory. Each difference sign represents a change in brightness between two pixels associated with a particular vector. A (+) represents a change from light to dark while a (-) represents a change from dark to light. For each pixel, the number of (+) difference signs and (-) difference signs are summed. Those pixels having a significant number of (+) signs greater than the number of (-) signs or a significant number of (-) signs greater than the number of (+) signs are assigned as edge points of the scanned image.