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en:processing:выделить_гарницы [2012/06/21 11:10] (current) Анна Протопопова created |
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| + | ===== Detect edges ===== | ||
| + | {{:processing:edge_detect.jpg|}} | ||
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| + | 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: | ||
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| + | * 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. | ||
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| + | In practice this algorithm works well with SPM images of rather big objects with distinct edges, for example, virus particles on mica surface: | ||
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| + | {{:processing:edge_detect_1.jpg|}} | ||
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| + | 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. | ||