Extract regions with equal gray values from an image.

::label_to_region segments an image into regions of equal gray value. One output region is generated for each gray value occuring in the image. This is similar to calling ::threshold multiple times, and accumulating the results with ::concat_obj. Another related operator is ::regiongrowing. However, ::label_to_region does not perform a ::connection operation on the resulting regions, i.e., they may be disconnected. A typical application of ::label_to_region is the segmentation of label images, hence its name.

The number of output regions is limited by the system parameter 'max_outp_obj_par', which can be read via

get_system(::'max_outp_obj_par':<Anzahl>) .

::label_to_region is not implemented for images of type 'real'. The input images must not contain negative gray values.

Let x1 be the minimum x-coordinate, x2 the maximum x-coordinate, y1 be the minimum y-coordinate, and y2 the maximum y-coordinate of a particular gray value. Furthermore, let N be the number of different gray values in the image. Then the runtime complexity is O(N * (x2 - x1 + 1) * (y2 - y1 + 1))

::label_to_region returns H_MSG_TRUE if the gray values lie within a correct range. The behavior 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.

::min_max_gray, ::sobel_amp, ::gauss_image, ::reduce_domain, ::diff_of_gauss

::connection, ::dilation1, ::erosion1, ::opening, ::closing, ::rank_region, ::shape_trans, ::skeleton

::threshold, ::concat_obj, ::regiongrowing, ::region_to_label

Region processing