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segment: m and b. The two dimensions of the accumulator array fro this family would
correspond to quantized values for b. the accumulator array accumulates evidence for the Faculty of Engineering Robotics Technology MECH 4041 16
B.Eng (Hons.) Mechatronics S. Venkannah Mechanical and Production Engineering Department existence of the line y= mx + b in bin A[M,B] where M and B are quantizations of m and b
respectively.
Using an accumulator array A, the Hough procedure examines each pixel and its neighborhood
in the image. It determines if there is enough evidence of an edge at that pixel, and if so
calculates the parameters of the specified curve that passes through this pixel. In the straight line
example with equation y= mx + b, it would estimate the m and the b of the line passing through
the pixel being considered if the measure of edged strength (such as gradient) as that pixel were
high enough. Once the parameters at a given pixel are estimated, they are quantized to
corresponding values M and B and the accumulator A[M,B] is incremented. Some schemes
increment by one and some by the strength of the gradient at the pixel being processed. After all
pixels have been processed, the accumulator array is searched for peaks. The peaks indicate the
parameters of the most likely lines in the image.
Consider the task of detecting a dark circle of a known radius r in an image with a uniform bright
background. The method starts with a search for dark image pixels; after such a pixel is found, a
locus of potential center points of the circle associated with it can be determined. Such a locus
of potential center points forms a circle with radius r. if the loci of potential circle centers are
constructed for all dark pixels identified in the original image, the frequency can be determined
with which each pixel of the image space occurs as an element of the circle center loci. The true
center of the circle being sought is represented by the pixel with the highest frequency of
occurrence in the circl...
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This document was uploaded on 03/12/2014 for the course MECHANICAL 214 at University of Manchester.
 Spring '14
 Mechatronics

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