added morphological filters (dilate, erode, open, close)

Finally, simple morphological filters have been added to VISFD. You can access them from within the filter_mrc program by using the -dilation, -erosion, -opening, and -closing arguments

From wikipedia:

"Together with closing, the opening serves in computer vision and image processing as a basic workhorse of morphological noise removal. Opening removes small objects from the foreground (usually taken as the bright pixels) of an image, placing them in the background, while closing removes small holes in the foreground, changing small islands of background into foreground. These techniques can also be used to find specific shapes in an image. Opening can be used to find things into which a specific structuring element can fit (edges, corners, ...)."

Binary morphological filters have not been implemented yet.

As mentioned before, these are grayscale filters, which are quite slow. Binary versions of these filters would be a lot faster, however I have not implemented them yet. In the meantime, the -dilation-gauss and -erosion-gauss filters are very fast and available (although they have artifacts near sharply curved surfaces at length-scales near the thickness parameter).