Cv2.error : (-215:Assertion failed) !_img.empty() in function 'imwrite'

Question

I am trying to segment images based on their label tag as helmet, non-helmet or unprocessed images for my project. But there is error saying image object is null. I have already made a secondary script where I processed over the same image which is working.I don't know why but it seems opencv library is unable to read one particular image. Any help will be really appreciated.

import requests
import shutil
import json
import sys
import os
import cv2
x=0
lis=[]
s=""
def batwara(filename,data):
    print("unproccesed/"+filename[6:])
    print(data)

    image = cv2.imread(filename)
    if image is None:
        print("NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN")
        return
    color = (255, 0, 0)
    thickness = 2
    totfaces = data['annotation']
    if totfaces is None:
        cv2.imwrite("unproccesed/"+filename[6:],image)
        return

    x=0
    for face in totfaces:
        x=x+1
        new_file=str(x)+filename[9:]
        print(new_file)
        label= face['label']
        print ("label=============",label)
        wid=face['imageWidth']
        hei=face['imageHeight']

        x1=int(face['points'][0]['x']*wid)
        y1=int(face['points'][0]['y']*hei)
        x2=int(face['points'][1]['x']*wid)
        y2=int(face['points'][1]['y']*hei)

        #print (x1,y1,x2,y2,wid,hei)
        start_point = (x1, y1)
        end_point = (x2, y2)
        crop_img = image[y1:y2, x1:x2]
        if len(label)==0:
            new_file= "unidentified/img"+new_file
            cv2.imwrite(new_file,crop_img)
        elif label[0] == "Without Helmet":
            new_file= "non_helmet/img"+new_file
            cv2.imwrite(new_file,crop_img)
        elif label[0] == "With Helmet":
            new_file= "helmet/img"+new_file
            cv2.imwrite(new_file,crop_img)






with open('/home/oem/Downloads/Bikers Wearing Helmet Or Not.json') as f:
    while True:
        c = f.read(1)
        s=s+c
        if c=='{' or c=='[':
            lis.append(c)
        if c==']'or c=='}':
                lis.pop()
                if len(lis)==0:
                    x=x+1
                    #print(filename)
                    #print(s)
                    data = json.loads(s)
                    filen,ex= os.path.splitext(data['content'])

                    filename= "image/img"+str(x)+ex
                    #print(data)
                    #print (data['content'])
                    # This is the image url.
                    image_url = data['content']
                    # Open the url image, set stream to True, this will return the stream content.
                    resp = requests.get(image_url, stream=True)
                    # Open a local file with wb ( write binary ) permission.
                    local_file = open(filename, 'wb')
                    # Set decode_content value to True, otherwise the downloaded image file's size will be zero.
                    resp.raw.decode_content = True
                    # Copy the response stream raw data to local image file.
                    shutil.copyfileobj(resp.raw, local_file)
                    # Remove the image url response object.
                    del resp

                    if ex!=".png":
                        batwara(filename,data)
                    s=""


        if not c:
            print ("End of file")
            print(x)
            break

The error displayed on the terminal is:

Traceback (most recent call last):
  File "app2.py", line 91, in <module>
    batwara(filename,data)
  File "app2.py", line 46, in batwara
    cv2.imwrite(new_file,crop_img)
cv2.error: OpenCV(4.2.0) /io/opencv/modules/imgcodecs/src/loadsave.cpp:715: error: (-215:Assertion failed) !_img.empty() in function 'imwrite'

Answer 1

You need to make sure that x1 == x2 or y1 == y2