Dilation is one of the fundamental operators in the mathematical morphology. It is usually applied to black and white images, but can also be applicable to grayscale ones. The basic effect of the operation is to gradually enlarge the boundaries of regions of foreground pixels (white pixels). Thus, areas of foreground pixels grow in size while holes within those regions become smaller. Applying this to the grayscale image will make bright objects larger, that is, the image will be lighter.

Both erosion and dilation work by translating the structuring element to various points in the input image, and examining the intersection between the translated kernel coordinates and the input image coordinates. For example, in the case of erosion, the output coordinate set consists of just those points to which the origin of the structuring element can be translated, while the element still remains entirely "within" the input image. In the case of erosion, the effect is the opposite.

For more information, see ImGearRasterProcessing.Dilate Method.