Filling Edges Using Flood Fill Not Working Properly

I am using openCV in python to detect cracks in concrete. I am able to use canny edge detection to detect cracks. Next, I need to fill the edges. I used floodfill operation of open

Solution 1:

I found the solution to what i was looking for. Posting it here as it might come of use to others. After some research on the internet, it was just 2 lines of codes as suggested in this : How to complete/close a contour in python opencv?

The code that worked for me is :

kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (9, 9))
dilated = cv2.dilate(image, kernel)
eroded=cv2.erode(dilated,kernel)

The result is in the image attached that shows before and after results.

Solution 2:

I see this so often here on SO, everybody wants to use edge detection, and then fill in the area in between the edges.

Unless you use a method for edge detection that purposefully creates a closed contour, detected edges will likely not form a closed contour. And you cannot flood-fill a region unless you have a closed contour.

In most of these cases, some filtering and a simple threshold suffice. For example:

import PyDIP as dip
import matplotlib.pyplot as pp

img = dip.Image(pp.imread('oJAo7.jpg')).TensorElement(1) # From OP's other question
img = img[4:698,6:]

lines = dip.Tophat(img, 10, polarity='black')
dip.SetBorder(lines, [0], [2])
lines = dip.PathOpening(lines, length=100, polarity='opening', mode={'robust'})
lines = dip.Threshold(lines, method='otsu')[0]

This result is obtained after a simple top-hat filter, which keeps only thin things, followed by a path opening, which keeps only long things. This combination removes large-scale shading, as well as the small bumps and things. After the filtering, a simple Otsu threshold yields a binary image that marks all pixels in the crack.

Notes:

• The input image is the one OP posted in another question, and is the input to the images posted in this question.
• I'm using PyDIP, which you can get on GitHub and need to compile yourself. Hopefully soon we'll have a binary distribution. I'm an author.