counting the number of objects in an image using python
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counting the number of objects in an image using python
I am trying to count the number of objects in this image:
I have a code for that:
import cv2
import numpy as np
image = cv2.imread('d:obj.jpg')
blurred = cv2.pyrMeanShiftFiltering(image,31,91)
gray = cv2.cvtColor(blurred,cv2.COLOR_BGR2GRAY)
ret , threshold = cv2.threshold(gray,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)
cv2.imshow("Threshold",threshold)
_, contours,_=cv2.findContours(threshold,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)
print "Number of contours: %d "%len(contours)
cv2.drawContours(image,contours,-1,(0,255,255),2)
cv2.namedWindow('Display',cv2.WINDOW_NORMAL)
cv2.imshow('Display',image)
cv2.waitKey()
the number of objects is 9, but the output is 1015.
when I try to show the the objects this is what I get:
How can I fix that?
thanks to all :)
I’m always baffled at all the problems people try to solve using contours. You don’t need contours in this case. It is cheaper to label the image (see connected component analysis). — Did you display the result of the threshold? Does it actually yield 9 objects? This is one of the nice things about image processing, you can easily examine the result of each step to see if you're headed in the right direction.
– Cris Luengo
Aug 9 at 20:23
@CrisLuengo yes I dispayed the result of threshold, it yields the objects in black dots on a white background
– Shlomi Elhaiani
Aug 9 at 21:50
Does it show each object as a single dot? I presume not. Also, if the background is white, it will consider the background as the object. You should invert the result of the threshold.
– Cris Luengo
Aug 9 at 22:05
1 Answer
1
You can easily get the area of contours. I would suggest putting up a threshold on area of contours. I mean to say iterate over all the contours and just keep only those which have area greater than a number specified by you and reject others. This way you can avoid small contours which are there due to noises.
number
thanks :) please see my answer below
– Shlomi Elhaiani
Aug 9 at 19:53
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I think you're mis-interpreting the meaning of countours: it's probably an image (i.e. an array of values) rather than the number of found objects.
– toti08
Aug 9 at 19:47