How to segment a large image parallely by dividing into subimages and merging to get final result

Hi

How to give an subimage to each worker, how to perform segmentation on each sub image parallely (for example region growing ,feature extraction,morphological operation etc.) and then merge the result to master process and produce the output i.e nothing but parallel processing.

Give me some idea whether we should use spmd or pmode or parfor or any other way to make parallel.