Edge detection and removal

I am new to Image Processing. I am developing a web application. I need t开发者_高级运维o take an image (free hand drawings) and remove parts of it. For example, take an image of cat and remove everything except its eye.

P.S-> I am developing a pictionary game based authentication system. It requires user to select an image co-relating his password, and I would morph it by detecting the edges and removing the parts of it and store it as a cue and display it to him, so that it makes sense only to him and not an attacker.

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Edge detection is done via a process called Convolution. There are various convolution matrixes defined, one of which is edge detection. You're going to have to look all that up, and also how to do convolution in Java: see java.awt.image.ConvolveOp for a start. How you then remove 'everything except' is another question.

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I don't have the entire code, but I had done edge detection using the approach defined [here] (http://www.pixastic.com/lib/docs/actions/edges2/). The removal of the parts was done using canvas methods