Fill the holes in OpenCV

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I have an edge map extracted from edge detection module in OpenCV (canny edge detection). What I want to do is to fill the holes in the edge map.

I am using C++, and OpenCV libraries. In OpenCV there is a cvFloodFill() function, and it will fill the holes with a seed (with one of the location to start flooding). However, I am trying to fill all the interior holes without knowing the seeds.(similar to imfill() in MATLAB)

Q1: how to find all the seeds, so that I could apply 'cvFloodFill()'?
Q2: how to implement a 'imfill()' equivalent?

Newbie in OpenCV, and any hint is appreciated.

flood-fill opencv image-processing matlab c++
9 Answers

Here's a quick and dirty approach:

  1. Perform canny on your input image so that the new binary image has 1's at the edges, and 0's otherwise
  2. Find the first 0 along a side of your edge image, and initiate a floodfill with 1's at that point on a blank image using your edge image as the mask. (We're hoping here that we didn't get unlucky and seed this first fill on the inside of a shape that is half-off the screen)
  3. This new floodfilled image is the 'background'. Any pixel here that has a 1 is the background, and any pixel that has a 0 is the foreground.
  4. Loop through the image and find any foreground pixels. Seed a floodfill on any you find.
  5. OR this new floodfilled image with your Canny image from step 1, and you're done.
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