METHOD AND APPARATUS FOR DETERMINING THE FINE ANGULAR ORIENTATION OF BAR CODE SYMBOLS IN TWO-DIMENSIONAL CCD IMAGES

A system for determining the fine angular orientation of a bar code symbol in a two-dimensional pixel image. A window is selected from the two-dimensional image for processing. Edge magnitude information and edge direction information are determined for a plurality of pixels in the selected window. For each pixel in the plurality of pixels, the edge magnitude and the edge direction of each pixel is associated with at least one of a plurality of directional ranges if the edge magnitude associated with the pixel exceeds a threshold. For each directional range in the plurality of directional ranges, a density value associated with each directional range is determined in accordance with the number of pixels associated with the directional range, an angular mean value is determined in accordance with the edge directions associated with the directional range, and a noise value is determined in accordance with the edge directions associated with the directional range. At least one candidate directional range is selected in accordance with the associated density values. The fine angular orientation of a bar code symbol is determined in accordance with the edge directions associated with the candidate directional range.