Edge detection: Difference between revisions

Revision as of 23:20, 18 February 2004

Revision as of 16:13, 19 February 2004

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Some other edge-detection operators are based upon the 2nd derivative of the intensity. This is essentially the rate of change in intensity gradient and is best at detecting lines :- as noted above, a line is a double edge, hence we will see an intensity gradient on one side of the line, followed immediately by the opposite gradient on the opposite site. Therefore we can expect to see a very high change in intensity gradient where a line is present in the image. To find lines, we can search the results for zero-crossings of the change in gradient.

If I(x) represents the intensity at point x, and I' '(x) is the second derivative at point x:

I' '(x) = 1.I(x-1) - 2.I(x) + 1.I(x+1)

Again most algorithms use a convolution mask to quickly process the image data: