Segment, dilate, and shrink a user defined domain on a figure

This function let the user segment, delate or shrink an irregular, possibly concave domain.

This program is useful for image segmentation, processing and registration. In particular, the metric of a registration in an iteration could be set to zero if it is outside the user defined area of interest. This will not only improve the efficiency but also the accuracy of registration by not considering the
image outside this domain.

User needs to input the name of image and the number of points needed to define the area, as well as the point(x,y) to be tested. User could dilate (when the value is positive) or shrink (when the
value is negative). Note that when the value is zero, then it returns the user defined polygonal domain (i.e. the segmentation). The image is a resin model of pelvis.

A special note for users in radiotherapy developers, this program will allow you to add a margin (i.e. dilation) to your user defined target to compensate for the registration in radiation treatment planning. See my challenge paper posted in Matlab Central on how to use it. Please contact me if you have questions. Please note that this implementation was done by ray tracing from the centroid.