detect stamps

edit

Hi I have many images with stamps and handwritten- signatures inside them.

With regards to signatures I have posted a question in the forum.

I want to detect present of stamps

stamps are of two types circular,rectangle(different orientation) and alignment is random. some of the stamps are colored and some are not I want detect and log if a stamp is present

approach1: 1. Converted the image to grayscale 2. Did a binary threshold on the image 3. Finding contours(not sure how to return a value saying yes circle or square is present)

after step 3 i am stuck even if i find a contour how do I know it is a stamp

approach2:

i am planning to get all images that look like a circle or square stamp and do a template matcing(Not sure if this is right approch)

Any suggestions appreciated

Thanks, C:\fakepath\sample4.jpg C:\fakepath\sample1.jpg C:\fakepath\sample3.jpg C:\fakepath\sample2.jpg