Abstract: Structures are identified in pixel data representative of a discrete pixel image and are differentiated from non-structures. The structures are identified by comparing gradient magnitudes with a selected gradient value and by comparing gradient directions of adjacent pixels. Pixels having desired relationships are counted and a focus parameter is applied to the resulting count. A final gradient threshold value is identified based upon the count and the focus parameter. The threshold value identifies structural pixels. Isolated adjacent regions may be eliminated from the structures. Edges defined by the structures are binary rank order filtered to arrive at the final structural definition. The structural and non-structural pixels may be further processed to enhance the image for subsequent display.