OpenCV Error: '(-215:Assertion failed) !_src.empty()' in cvtColor() - Troubleshooting Guide

This error occurs when the input image (_src) is empty or null. This means that the function 'cvtColor()' is not able to convert the color space of the image because there is no image data to convert.

To resolve this error, you can check if the input image is loaded correctly and is not empty. You can do this by checking the dimensions or size of the image before passing it to the 'cvtColor()' function.

For example:

import cv2

# load the input image
img = cv2.imread('image.jpg')

# check if the image is loaded correctly
if img is not None and img.size > 0:
    # convert the color space of the image
    img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
else:
    print('Error: Failed to load or empty image')

In the above example, we first check if the image is loaded correctly and is not empty by checking its size. If the image is not empty, we then convert its color space to grayscale using the 'cvtColor()' function. If the image is empty or not loaded correctly, we print an error message.