Applies a Sobel filter to the data in the two-dimensional array Data and writes the results back to Data. The parameter PixMask contains an optional pixel mask which controls which cells of the array Data should be processed. A TRUE value excludes the corresponding cell from calculations. Set PixMask to NIL if you do not need the masking feature.
The function returns the following error codes:
0 .... everything is OK
-1 ... the dimensions of Data and PixMask do not match