How to extract shape characteristics from an image?

Hi, I am working on abnormal activity detection. I have image frames which represent various activities of person. I want to extract the shape descriptors from these images.I don't understand how to do that. Can someone please help me? I have attached the image from which I have to extract the features. How can I achieve that?

[Satyajeet Sasmal]

Below is a ML File Exchange function that might be useful.

http://www.mathworks.com/matlabcentral/fileexchange/35038-descriptor-for-shapes-and-letters--feature-extraction-

-Satya

Answer 1

[Muhammad Usman Saleem]

read my answer and @image answer here for this question

http://www.mathworks.com/matlabcentral/answers/270867-set-the-outside-pixel-values-into-zero

Answer 2

[Dima Lisin]

regionprops function in the Image Processing Toolbox can compute various shape characteristics of regions, such as area, perimeter, principal axes, etc.