opencv cv2.imread()报错： error: (-215:Assertion failed) !_src.empty() in function ‘cv::cvtColor‘

Problem:
When using opencv in pycharm, an error is reported when executing cv2.imread(filepath) to read pictures:
cv2.error: OpenCV(4.7.0) D:\a\opencv-python\opencv-python\opencv\modules\imgproc\src \color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

Solution:
Try the following methods:
1. Check whether there is Chinese in the picture path, try to Do not include Chinese, if there is any, modify it
2. Change the "\" in the picture path to "/";

# filepath = 'D:\flower\picture\yzm1.bmp' # 这么写会报错
filepath = 'D:/flower/picture/yzm1.bmp'
#  1.图片处理
# 1)先读入图片，并将图片转成灰度图
im = cv2.imread(filepath)
im_gray = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)

3. Check the picture path, not to the folder, but to the specific file name
4. Check whether the file name suffix of the picture is correct (.jpg, .bmp, etc.)

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