Erode a region with a rectangular structuring element.

erosion_rectangle1 applies an erosion with a rectangular structuring element to the input regions Region. The size of the structuring rectangle is Width x Height. The operator results in reduced regions, and the areas smaller than the rectangular mask are eliminated.

erosion_rectangle1 is a very fast operation because the height of the rectangle enters only logarithmically into the runtime complexity, while the width does not enter at all. This leads to excellent runtime efficiency, even in the case of very large rectangles (edge length > 100).

Regions containing small connecting strips between large areas are separated only seemingly. They remain logically one region.

To reduce a region by the same amount in all directions, Width and Height must be odd. If this is not the case, the region is eroded by a larger amount at the right or at the bottom, respectively, than at the left or at the top.

Let F1 be the area of an input region and H be the height of the rectangle. Then the runtime complexity for one region is:

       O(sqrt(F1) * ld(H)) .

erosion_rectangle1 returns 2 (H_MSG_TRUE) if all parameters are correct. The behavior in case of empty or no input region can be set via:

  a) no region:    set_system('no_object_result',<RegionResult>)
  b) empty region: set_system('empty_region_result',<RegionResult>)

erosion_rectangle1 is reentrant and automatically parallelized (on tuple level).

threshold, regiongrowing, watersheds, class_ndim_norm

reduce_domain, select_shape, area_center, connection

erosion1, minkowski_sub1

gen_rectangle1

Foundation