How to recognize rectangles in this image?

Question

I have a image with horizontal and vertical lines. In fact, this image is the BBC website converted to horizontal and vertical lines. My problem is that I want to be able to

Answer 1

There are several different approaches to your problem. I'd use a morphological image processing tool like this one. You will have the flexibility to define "rectangle" even something that not "exactly closed" (where the fill algorithm will fail).

Another possibility could be to use a machine learning approach, which basically is more data-driven than definition-driven like the previous one. You'll have to give your algorithm several "examples" of what a rectangle is, and it will eventually learn (with a bias and an error rate).