Tutorial

Erode / dilate filter

Erode filter is used to remove bright regions or expand dark regions whereas Dilate filter is useful to remove dark regions or expand bright regions. See the following sample images.

Original image

B33 Horse head and Flame Nebula  (Courtesy by Jim Gage, http://dirtclodobservatory.com/)

Dilate filter applied         * Menu > Processing > Erode > 5x5

* Bright regions (stars) are expanded

Erode filter applied         * Menu > Processing > Erode > 5x5

* Bright regions (stars) were disappeared.