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Hough Circles way too Sensitive

Hi,

I just downloaded OpenCV today. I decided to give it a test on a really simple example.

So I did Hough Circles on this simple image: image description

And I implemented Hough Circle using python :

image description

However, I got a very messy circle detection with too many circles!

image description

I must be doing something wrongly! Could you tell me what it is?

Thanks very much!

Hough Circles way too Sensitive

Hi,

I just downloaded OpenCV today. I decided to give it a test on a really simple example.

So I did Hough Circles on this simple image: image description

And I implemented Hough Circle using python :

image descriptionimport cv2 import numpy as np

img = cv2.imread('a_circle.jpg',0)

gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

cimg = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)

bin=cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

invbin=cv2.bitwise_not(bin)

edges = cv2.Canny(img,50,150,apertureSize = 3) circles = cv2.HoughCircles(edges,cv2.HOUGH_GRADIENT,1,20,param1=50,param2=30,minRadius=100,maxRadius=0) cv2.imshow('edge',edges) cv2.waitKey(0) circles = np.uint16(np.around(circles)) for i in circles[0,:]: # draw the outer circle cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),2) # draw the center of the circle cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3)

cv2.imshow('detected circles',cimg) cv2.waitKey(0) cv2.destroyAllWindows()

However, I got a very messy circle detection with too many circles!

image description

I must be doing something wrongly! Could you tell me what it is?

Thanks very much!

Hough Circles way too Sensitive

Hi,

I just downloaded OpenCV today. I decided to give it a test on a really simple example.

So I did Hough Circles on this simple image: image description

And I implemented Hough Circle using python :

import cv2 import numpy as np

img = cv2.imread('a_circle.jpg',0)

gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

cimg = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)

bin=cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

invbin=cv2.bitwise_not(bin)

edges = cv2.Canny(img,50,150,apertureSize = 3) circles = cv2.HoughCircles(edges,cv2.HOUGH_GRADIENT,1,20,param1=50,param2=30,minRadius=100,maxRadius=0) cv2.imshow('edge',edges) cv2.waitKey(0) circles = np.uint16(np.around(circles)) for i in circles[0,:]: # draw the outer circle cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),2) # draw the center of the circle cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3)

cv2.imshow('detected circles',cimg) cv2.waitKey(0) cv2.destroyAllWindows()

However, I got a very messy circle detection with too many circles!

image description

I must be doing something wrongly! Could you tell me what it is?

Thanks very much!

Update:

I changed minDistance from 20 to 50 and I got:

image description

Update 2:

I changed minDistance from 50 to 120 and I got:

The problem has been solved. Thanks sjhalayka!!

click to hide/show revision 4
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updated 2018-06-01 07:37:39 -0500

berak gravatar image

Hough Circles way too Sensitive

Hi,

I just downloaded OpenCV today. I decided to give it a test on a really simple example.

So I did Hough Circles on this simple image: image description

And I implemented Hough Circle using python :

import cv2
import numpy as np

np img = cv2.imread('a_circle.jpg',0)

gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

cv2.imread('a_circle.jpg',0) #gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) cimg = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)

bin=cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1]

invbin=cv2.bitwise_not(bin)

cv2.cvtColor(img,cv2.COLOR_GRAY2BGR) #bin=cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU)[1] #invbin=cv2.bitwise_not(bin) edges = cv2.Canny(img,50,150,apertureSize = 3) circles = cv2.HoughCircles(edges,cv2.HOUGH_GRADIENT,1,20,param1=50,param2=30,minRadius=100,maxRadius=0) cv2.imshow('edge',edges) cv2.waitKey(0) circles = np.uint16(np.around(circles)) for i in circles[0,:]: # draw the outer circle cv2.circle(cimg,(i[0],i[1]),i[2],(0,255,0),2) # draw the center of the circle cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3)

cv2.circle(cimg,(i[0],i[1]),2,(0,0,255),3) cv2.imshow('detected circles',cimg) cv2.waitKey(0) cv2.destroyAllWindows()

cv2.destroyAllWindows()

However, I got a very messy circle detection with too many circles!

image description

I must be doing something wrongly! Could you tell me what it is?

Thanks very much!

Update:

I changed minDistance from 20 to 50 and I got:

image description

Update 2:

I changed minDistance from 50 to 120 and I got:

The problem has been solved. Thanks sjhalayka!!