how to find the centre

I am working on palm print recognisation,and I have done the following steps

1)Applying a low pass filter,

2)converting into binary

next i have to do following steps

1)Obtain the boundaries of the gaps and

2)Compute the tangent of the two gaps.

can anyone tell how to process

[Image Analyst]

I don't see what that has to do with finding the centre. Uploading an image and a script and better explanation of what you want to do would help.

[FIR]

THERE ARE SIX IMAGES ,I WANT TO PERFORM OPERATION AS IN FIGURE c AND d CAN U TELL HOW TO PROCESS PLEASE

http://imgur.com/Y8B0d