Btukfyl

i m running this code but i m getting an error

cv2.drawContours(image,contours,-1,(0,255,0),3)



error: OpenCV(3.4.3) D:BuildOpenCVopencv-3.4.3modulesimgprocsrcdrawing.cpp:2511: error: (-215:Assertion failed) npoints > 0 in function 'cv::drawContours'

import cv2

import numpy as np



image=cv2.imread("C:/Users/AnushkaGupta/Desktop/image database/input1.jpg")

cv2.imshow("original image",image)

cv2.waitKey(0)



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



edged=cv2.Canny(gray,30,200)

cv2.imshow("Canny Edges",edged)

cv2.waitKey(0)



contours,hierarchy, _=cv2.findContours(edged,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)

cv2.imshow("canny Edges After Contouring",edged)

cv2.waitKey(0)



print("Number of Contours found ="+str(len(contours)))







cv2.drawContours(image,contours,-1,(0,255,0),3)



cv2.imshow("Contours",image)

cv2.waitKey(0)

cv2.destroyAllWindows()

When you collect the output of findContours(), the order should be as follows:

image, contours, hierarchy = cv2.findContours(...)

In your specific case you should write (I omitted the imshow steps):

import cv2

import numpy as np



image = cv2.imread("./input1.jpg")



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



edged = cv2.Canny(gray, 30, 200)



_, contours, hierarchy = cv2.findContours(edged, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)



print(f"Number of Contours found = {len(contours)}")



cv2.drawContours(image, contours, -1, (0,255,0), 3)