nonmax_suppression_amp ( ImgAmp : ImageResult : Mode : )

Suppress non-maximum points on an edge.

nonmax_suppression_amp suppresses all points in the regions of the image ImgAmp for which the gray values are no local (directed) maximum. In contrast to nonmax_suppression_dir, no direction image is needed. Two modes of operation can be selected:

   'hvnms'
           A point is labeled as a local maximum if its gray value
           is larger than or equal to the gray values within a seach
           space of +/- 5 pixels, either horzontally or vertically.
           Non-maximum points are removed from the region, gray
           values remain unchanged.

   'loc_max'
           A point is labeled as a local maximum if its gray value
           is larger than or equal to the gray values of its eight
           neighbors.


Parameters

ImgAmp (input_object)
image(-array) -> object : byte
Amplitude (gradient magnitude) image.

ImageResult (output_object)
image(-array) -> object : byte
Image with thinned edge regions.

Mode (input_control)
string -> string
Select horizontal/vertical or undirected NMS.
Default value: 'hvnms'
List of values: 'hvnms', 'loc_max'


Result

nonmax_suppression_amp returns TRUE if all parameters are correct. The behaviour with respect to the input images and output regions can be determined by setting the values of the flags 'no_object_result', 'empty_region_result', and 'store_empty_region' with set_system. If necessary, an exception is raised.


Possible Predecessors

sobel_amp


Possible Successors

threshold__, hysteresis_threshold__


Alternatives

grey_skeleton__, local_max, max1__


See also

skeleton


References

S.Lanser: "Detektion von Stufenkanten mittels rekursiver Filter nach Deriche"; Diplomarbeit; Technische Universität München, Institut für Informatik, Lehrstuhl Prof. Radig; 1991.

J.Canny: "Finding Edges and Rows in Images"; Report, AI-TR-720; M.I.T. Artificial Intelligence Lab., Cambridge, MA; 1983.



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