4

I need to find the coordinates of the largest empty rectangle in a PNG image. The rectangle should consist of light colors (if that is too difficult, white pixels only are fine) and should be axis-oriented.

I am new to computer vision and I found out about OpenCV, I am currently using the python interface to it and started tackling this problem with the SimpleBlobDetector interface, but it gives me only the center of the Blob with a certain radius.

Can anyone point me in the right direction for this?

EDIT: I need to do this with a regular colored PNG image, not a binary matrix

Sascha Mayr
  • 341
  • 4
  • 16
  • 2
    Possible duplicate of [Find largest rectangle containing only zeros in an N×N binary matrix](http://stackoverflow.com/questions/2478447/find-largest-rectangle-containing-only-zeros-in-an-n%c3%97n-binary-matrix) – Miki Jan 17 '16 at 15:17
  • 1
    In response to your edit, you need to convert your color image to grayscale and apply a threshold in order to separate the "light colors" from the others, anyway. I think @Miki's duplicate should work. – beaker Jan 19 '16 at 15:53

1 Answers1

1

You can use a contour extractor, with the given point list you can check the size of the rectangle by checking the sizes of the lists, assuming that all the rectangles are parallel to the cardinal axis. If not you need to compute the distance of a pixel and the next for all the pixels in the contour list by using the x and y coordinates on each.

Alexander Leon VI
  • 499
  • 1
  • 4
  • 18