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Performs a morphological dilation on a region using a predefined kernel.

Name Type Range Description
inRegion Region Input region
inKernel KernelShape Kernel shape (predefined)
inRadiusX Integer 0 - Nearly half of the kernel's width (2*R+1)
inRadiusY Integer* 0 - Nearly half of the kernel's height (2*R+1), or same as inRadiusX
outRegion Region Output region


Making the region thicker or filling-in small holes within it.


The operation performs a morphological dilation, which is a basic tool used for region expansion. Similarly to other region morphology operations, dilation is conducted using a shape called kernel (or structuring element). The kernel is repeatedly centered at each location within the dimensions of the input region. Then, pixel location L is added to the resulting region if and only if at least one of the input region pixels lies inside the kernel centered at this (L) location.

The input parameter inKernel allows to choose the shape of a kernel, while parameters inRadiusX, inRadiusY allow to determine its dimensions. For instance:

  • inKernel = Ellipse together with inRadiusX = inRadiusY results in expansion performed equally in all directions.
  • Setting inRadiusX to higher value than inRadiusY results in expansion performed more significantly along horizontal axis.


  • Increase inRadiusX to make the output region thicker.
  • Change inKernel to Ellipse to make the filter work equally strongly in each direction (execution will be slower).


Description of usage of this filter can be found in examples and tutorial: Capsules, Mounts (Contour Analysis), OCR Read Number (SVM), Brick destroy (Game), Mounts (Segmentation), Comparing Golden Template.

DilateRegion run with inKernel = Ellipse of dimensions inRadiusX = 5, inRadiusY = 5.


This filter can throw an exception to report error. Read how to deal with errors in Error Handling.

List of possible exceptions:

Error type Description
DomainError Unsupported kernel in DilateRegion.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of DilateRegion filter group.

See Also

  • CloseRegion – Performs a morphological closing on a region using selected predefined kernel.
  • ErodeRegion – Performs a morphological erosion on a region using a predefined kernel.