Canny operator
Canny operator an edge detector devised by john canny as the optimal solution to a variational problem with three constraints. The general solution obtained numerically can be approximated in practical contexts by the first derivative of a gaussian. Canny operator usually refers to the extension to two dimensions of this approximation, i.E., To use of a set of oriented operators whose orthogonal cross sections are a gaussian and the derivative of a gaussian. Its advantage is its capability for allowing edges and their orientations to be detected to sub-pixel accuracy. It uses a convolution with a gaussian to reduce noise and a derivative to enhance edges in the resulting smoothed image. The two are combined into one step — a convolution with the derivative of a gaussian. A hysteresis thresholding stage is included, to allow closed contours to remain closed.
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Author of the text: Ed. P.A. Laplante Boca Raton: CRC Press LLC, 2000
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