OpenCV 4.4.0 错误：（-215：断言失败）._img:empty() 在 function 'cv::imwrite'

Question

I want to detect circles in a few images and have these images cropped. The following code gives the error addressed in the title. What makes me wonder is that the first picture in my input folder is actually being cropped accordingly even though the error is still being displayed. Any other images in the same folder are being ignored though (probably bc the error message interrupts the loop?)

I already added the "print(images)" line in order to assure that the input folder actually contains all the required images and it successfully does print the names of the images in the chosen folder.

Can anyone help me sorting this issue out?

If any additional information is required or if this question was too inaccurate, please let me know!

img_raw = r'C:/Users/Chris/Documents/Extrahierte Bilder/Beispiel' # raw images
img_circles = r'C:/Users/Chris/Documents/Extrahierte Bilder/Beispiel' # cropped circles

images = os.listdir(img_raw)
print(images)

for image in images:

# define output name
output_name = 'cropped_' + str(image)
# define path to image:
path = str(img_raw) + '/' + str(image)
# read image:
image = cv2.imread(path)
# create copy of image:
output = image.copy()
# convert copy to gray scale
gray = cv2.cvtColor(output, cv2.COLOR_BGR2GRAY)

# detect circles in the image
circles = cv2.HoughCircles(gray, cv2.HOUGH_GRADIENT, 1.2, 800)

if circles is not None:
    
    for c in circles[0, :]:
        c = c.astype(int)
        # crop the image:
        crop = gray[c[1]-c[2]:c[1]+c[2], c[0]-c[2]:c[0]+c[2]]
        # write cropped image to file:
        cv2.imwrite(img_circles + '/' + str(output_name), crop)    
                    
else:
    
    print('No circle(s) detected for ' + str(image))

Answer 1

things you need to attention, space can not exist in your file path, using os.sep repalce '/' may works.