By using the Opening transformation (dilatation of image erosion) firstly, it is necessary to apply erode (narrowing) to the image, and then dilate (widening). By that, the image can be black and white or halftone.
The filter deletes small light details in the image, preserving general brightness of the large details. It smoothes and deletes the noises, and helps to get rid of all fragments sticking out of the area near its border. Mostly this transformation is used for aligning non-uniform lighting of the image background.
Closing is also applied for counting the parts on a binary (black and white) image. For example, after threshold transformation of an image with the help of the filter it is possible to count the amount of particles placed nearer to each other, before counting the parts.
Size (size) parameter indicates the circle of the filter influence around each point.
Iteration (iteration) parameter indicates the amount of iterations.