MACHINE VISION METHOD AND APPARATUS FOR EDGE-BASED IMAGE HISTOGRAM ANLAYSIS

A system for edge-based image histogram analysis permits identification of predominant characteristics of edges in an image. The system includes an edge detector that generates an edge magnitude image having a plurality of edge magnitude values based on pixels in the input image. The edge detector can be a Sobel operator that generates the magnitude values by taking the derivative of the input image values, i.e., the rate of change of intensity over a plurality of image pixels. A mask generator creates a mask based upon the values output by the edge detector. The mask can be used for masking input image values that are not in a region for which there is a sufficiently high edge magnitude. A mask applicator applies the pixel mask array to a selected image, e.g., the input image or an image generated therefrom (such as an edge direction image of the type resulting from application of a Sobel operator to the input image). A histogram generator generates a histogram of the pixel values in the masked image, i.e., a count of the number of image pixels that pass through the mask. A peak detector identifies the intensity value in the histogram that represents the predominant image intensity value (image segmentation threshold) or predominant edge direction values associated with the edge detected by the edge detector.