Detecting edges of a card with rounded corners

Question

Hi currently i am working on an OCR reading app where i have successfully able to capture the card image by using AVFoundation framework.

For next step, i need to fi

Answer 1

instead of "pure" rectangular blobs, try to go for nearly rectangular ones.

1- gaussian blur

2- grayscale and canny edge detection

3- extract all blobs (contours) in your image and filter out small ones. you will use findcontours and contourarea functions for that purpose.

4- using moments, filter out non-rectangular ones. First you need to check out moments of rectangle-like objects. You can do it by yourself or google it. Then list those moments and find similarity between objects, create your filter as such.

Ex: After test, say you found out central moment m30's are similar for rectangle-like objects -> filter out objects having inaccurate m30.