How could I make the discontinuous contour of an image consistant?

Question

In the task, I got an discontinuous edge image, how could make it closed? in other word make the curve continuous. And the shape could be any kind, cause this the coutour shadow

Answer 1

Mark Setchell's answer is a fun way to learn new stuff along the way. My approach is rather simple and straight-forward.

I got the following solution off the top of my head. It involves a simple blurring operation sandwiched between two morphological operations

I have explained what I have done alongside the code:

#---- I converted the image to gray scale and then performed inverted binary threshold on it. ----

img = cv2.imread('leaf.jpg')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret, thresh = cv2.threshold(gray, 127, 255, 1)  

#---- Next I performed morphological erosion for a rectangular structuring element of kernel size 7 ----

kernel = np.ones((7, 7),np.uint8)
erosion = cv2.morphologyEx(thresh, cv2.MORPH_ERODE, kernel, iterations = 2)
cv2.imshow('erosion', erosion )

#---- I then inverted this image and blurred it with a kernel size of 15. The reason for such a huge kernel is to obtain a smooth leaf edge ----

ret, thresh1 = cv2.threshold(erosion, 127, 255, 1)
blur = cv2.blur(thresh1, (15, 15))
cv2.imshow('blur', blur)

#---- I again performed another threshold on this image to get the central portion of the edge ----

ret, thresh2 = cv2.threshold(blur, 145, 255, 0)

#---- And then performed morphological erosion to thin the edge. For this I used an ellipse structuring element of kernel size 5 ----

kernel1 = cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(5,5))
final = cv2.morphologyEx(thresh2, cv2.MORPH_ERODE, kernel1, iterations = 2)
cv2.imshow(final', final)

Hope this helps :)