Asymmetric boundary - Image Processing

Hi, I've got this project where I grade cashews based on their color and size and I have written a code which does that too. I have used the concept of bounding boxes to extract a single cashew from an image containing multiple cashews. This posed a problem in that I have parts of neighboring cashews getting included in another cashew 'Bounding box'. I have attached an extracted cashew image and the original image from which it was extracted for reference. My question is; is there any technique for an asymmetric boundary rather than a symmetric boundary like a bounding box? It would do me good if there was a technique to get a boundary that goes around the cashew so that there would be no invasions from neighboring cashews. Thank you for your help!

Note: I have used regionstats (with bounding box attribute) and imcrop to extract cashews.

[Walter Roberson]

duplicates http://uk.mathworks.com/matlabcentral/answers/260095-asymmetric-boundary-image-processing