Opening is another operation from mathematical morphology that is derived from the fundamental operations of erosion and dilation. Like those operators, it is usually applied to black and white images, but can be applicable to grayscale images as well. The basic effect of an opening is somewhat like erosion in that it tends to remove some of the foreground (bright) pixels from the edges of regions of foreground pixels. However it is less destructive than erosion in general. As with other morphological operators, the exact operation is determined by a structuring element. The effect of the operator is to preserve foreground regions that have a similar shape to this structuring element, or that can completely contain the structuring element, while eliminating all other regions of foreground pixels.

For more information, see the IG_IP_open function.