Python line giving error

[raajeshsiingh]

(-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S)

This line is giving the following error...

error: OpenCV(4.1.2) C:\projects\opencv-python\opencv\modules\imgproc\src\shapedescr.cpp:274: error: (-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S) in function 'cv::contourArea'

[aashrith2021]

(-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S)

This line is giving the following error...

error: OpenCV(4.1.2) C:\projects\opencv-python\opencv\modules\imgproc\src\shapedescr.cpp:274: error: (-215:Assertion failed) npoints >= 0 && (depth == CV_32F || depth == CV_32S) in function 'cv::contourArea'

do not change the code... just u need to uninstall the opencv 4x pip uninstall opencv-python and try installing pip install opencv-python==3.4.9.31

[swetabhmukherjee]

A simple version of the code:

`import cv2 import matplotlib.pyplot as plt

img=cv2.imread('car4.jpeg') cv2.imshow('image',img) cv2.waitKey(0) cv2.destroyAllWindows() plt.imshow(img)

mg = cv2.resize(img, (620,480) ) gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) #convert to grey scale cv2.imshow('gray image',gray) cv2.waitKey(0) cv2.destroyAllWindows()

bilateral filtering

gray = cv2.bilateralFilter(gray, 11, 17, 17) cv2.imshow('bilaeral image',gray) cv2.waitKey(0) cv2.destroyAllWindows()

edge detection

edged = cv2.Canny(gray, 30, 200) #Perform Edge detection cv2.imshow('edge detection',edged) cv2.waitKey(0) cv2.destroyAllWindows()

import imutils cnts = cv2.findContours(edged.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE) cnts = imutils.grab_contours(cnts) cnts = sorted(cnts, key = cv2.contourArea, reverse = True)[:10] screenCnt = None

loop over our contours

for c in cnts:

approximate the contour

peri = cv2.arcLength(c, True)
approx = cv2.approxPolyDP(c, 0.018 * peri, True)
# if our approximated contour has four points, then # we can assume that we have found our screen
if len(approx) == 4:
    screenCnt = approx 
    break

import numpy as np

Masking the part other than the number plate

mask = np.zeros(gray.shape,np.uint8) new_image = cv2.drawContours(mask,[screenCnt],0,255,-1,) new_image = cv2.bitwise_and(img,img,mask=mask)

Now crop

(x, y) = np.where(mask == 255) (topx, topy) = (np.min(x), np.min(y)) (bottomx, bottomy) = (np.max(x), np.max(y)) Cropped = gray[topx:bottomx+1, topy:bottomy+1]

show number plate image

cv2.imshow('img',new_image) cv2.waitKey(0) cv2.destroyAllWindows() plt.imshow(new_image)

show cropped image

cv2.imshow('img',Cropped) cv2.waitKey(0) cv2.destroyAllWindows() plt.imshow(Cropped) cv2.imwrite('plate.jpg',img)`

[pawneshtapish]

Just change line 28 cnts=sorted(new, key = cv2.contourArea, reverse = True)[:30]