Extract watershed basins from an image using a threshold.
The operator watersheds_threshold segments regions (basins) that are separated from each other by a watershed that has a height of at least Threshold.
In the first step, watersheds_threshold computes the watersheds without applying a threshold, resulting in the same basins that would be obtained when calling watersheds (for more details please refer to the description of watersheds). In the second step, the basins are successively merged if they are separated by a watershed that is smaller than Threshold. Let B1 and B2 be the minimum gray values of two neighboring basins and W the minimum gray value of the watershed that separates the two basins. The watershed is eliminated and the two basins are merged if
max{W-B1,W-B2} < Threshold.
The thus obtained basins are returned in Basins.
If Threshold is set to 0, watersheds_threshold is comparable to watersheds except that no watersheds but only expanded basins are returned. If Threshold is set to the maximum gray value range of Image then no two basins are separated by a watershed exceeding Threshold, and hence, Basins will contain only one region.
|
Image (input_object) |
image -> object : byte / uint2 / real |
| Image to be segmented. | |
|
Basins (output_object) |
region-array -> object |
| Segments found (dark basins). | |
|
Threshold (input_control) |
number -> integer / real |
| Threshold for the watersheds. | |
| Default value: 10 | |
| Suggested values: 0, 5, 10, 20, 30, 50 | |
| Restriction: Threshold >= 0 | |
watersheds always returns 2 (H_MSG_TRUE). The behavior with respect to the input image 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.
watersheds_threshold is reentrant and processed without parallelization.
gauss_image, smooth_image, invert_image
expand_region, select_shape, reduce_domain, opening
Foundation
