The following procedure is used to perform the interpolation:
1. There are 2 ROIs, StartROI and EndROI. Note that both the ROIs are always polygons. Interpolation is done by interpolating the polygon ROIs and then converting the polygons to masks using the 'poly2mask' function.
2. At first, we downsample/upsample the 2 ROIs so that both the ROIs have same number of points.
3. The next step is to match the orientation of 2 ROIs so that there is minimum displacement between the 2 ROIs. This is done by re-ordering the points of the polygon ROI object. This is an important step as it ensures that in the next interpolation steps the interpolated ROIs don't fold over themselves.
4. Once the orientations of the 2 ROIs match, the interpolation is straightforward. We just add/substract a factor of delta (end-start) to the StartROI positions to get the ROI positions for the intermediate slices.
