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en:processing:выделить_гарницы [2012/06/21 11:10] (current)
Анна Протопопова created
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 +===== Detect edges =====
 +This function detects edges of objects using [[http://​en.wikipedia.org/​wiki/​Canny_edge_detector|Canny algorithm]]. This algorithm is considered to be the best to detect edges on noisy images. The algorithm consists of:
 +  * Noise Reduction;
 +  * Gradient Calculation;​
 +  * Non-Maximum Suppression which chooses only the points of gradient local maximum in the direction of gradient vector to be pixels of the edges;
 +  * Threshold Analysis and final selection of the edges.
 +In practice this algorithm works well with SPM images of rather big objects with distinct edges, for example, virus particles on mica surface:
 +When the function is called up from [[меню_математика|Mathematics menu]] a setting window appears where threshold value and noise level must be specified as a fraction of 1.