Operator Reference

watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker (Operator)

watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker — Extract watersheds and combine basins based on markers.

Signature

watersheds_marker(Image, Markers : Basins : : )

Description

watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker segments an image based on the topology of the gray values and returns the resulting regions in BasinsBasinsBasinsbasinsbasins. The image is interpreted as a “mountain range”. Higher gray values correspond to “mountains”, while lower gray values correspond to “valleys”. The image, interpreted in this particular way, is flooded, starting with the regions defined in MarkersMarkersMarkersmarkersmarkers, until the entire image is filled. Thus, each pixel is assigned to the marker to which it has the path with the lowest maximum height. If this is the case for multiple markers, the pixel is assigned to either of them.

The resulting basins, one per input region in MarkersMarkersMarkersmarkersmarkers, are returned in BasinsBasinsBasinsbasinsbasins. Note that some of those regions might be empty. This can happen if, for example, two marker regions are in the same watershed basin. If a pixel is contained in multiple marker regions, only the last marker region is used as seed for that pixel. It is advised that the marker regions do not overlap.

The flooding is performed only for the domain of ImageImageImageimageimage. Parts of the marker regions outside the domain of ImageImageImageimageimage are ignored.

It is advisable to apply a smoothing operator (e.g., binomial_filterbinomial_filterBinomialFilterBinomialFilterbinomial_filter or gauss_filtergauss_filterGaussFilterGaussFiltergauss_filter) to the input image before calling watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker. To segment an image, it is also often reasonable to run an edge extractor (such as edges_imageedges_imageEdgesImageEdgesImageedges_image or edges_coloredges_colorEdgesColorEdgesColoredges_color) on the image, and pass the resulting amplitude image to watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker.

Attention

If the image contains many fine structures or is noisy, many watershed regions need to be processed internally, and thus the runtime increases considerably.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Processed without parallelization.

Parameters

ImageImageImageimageimage (input_object) singlechannelimage → object (byte / uint2 / real)

Input image.

MarkersMarkersMarkersmarkersmarkers (input_object) region-array → object

Initial markers from which to flood the image.

BasinsBasinsBasinsbasinsbasins (output_object) region-array → object

Basins for all markers.

Example (HDevelop)

read_image (Image, 'printer_chip/printer_chip_01')
edges_image (Image, ImaAmp, ImaDir, 'canny', 1, 'nms', 20, 40)

* Compute background marker
full_domain (ImaAmp, ImageFull)
erosion_circle (Image, RegionErosion, 2.5)
difference (Image, RegionErosion, Boundary)

* Compute foreground markers
threshold (Image, Region, 200, 255)
erosion_circle (Region, RegionErosion1, 7.5)
connection (RegionErosion1, ConnectedRegions)
select_shape (ConnectedRegions, SelectedRegions, 'area', 'and', 1500, 99999)

* Apply marker-based watersheds
concat_obj (Boundary, SelectedRegions, MarkerRegions)
watersheds_marker (ImageFull, MarkerRegions, Basins)

* Display results
dev_display (Image)
dev_set_color (['#FF000055', '#00FF0055', '#0000FF55', '#FF00FF55', \
                '#FFFF0055', '#00FFFF55', '#80FF0055', '#0080FF55'])
dev_display (MarkerRegions)
dev_set_draw ('fill')
dev_display (Basins)

Result

If all input parameters are valid, watersheds_markerwatersheds_markerWatershedsMarkerWatershedsMarkerwatersheds_marker returns 2 ( H_MSG_TRUE) . If necessary, an exception is raised.

Possible Predecessors

binomial_filterbinomial_filterBinomialFilterBinomialFilterbinomial_filter, gauss_filtergauss_filterGaussFilterGaussFiltergauss_filter, smooth_imagesmooth_imageSmoothImageSmoothImagesmooth_image, invert_imageinvert_imageInvertImageInvertImageinvert_image, edges_imageedges_imageEdgesImageEdgesImageedges_image

Possible Successors

expand_regionexpand_regionExpandRegionExpandRegionexpand_region, select_shapeselect_shapeSelectShapeSelectShapeselect_shape, reduce_domainreduce_domainReduceDomainReduceDomainreduce_domain, openingopeningOpeningOpeningopening

Alternatives

watershedswatershedsWatershedsWatershedswatersheds, pouringpouringPouringPouringpouring, watersheds_thresholdwatersheds_thresholdWatershedsThresholdWatershedsThresholdwatersheds_threshold

Module

Foundation

Operators