cv2.error: OpenCV(4.5.2) resize.cpp:4051: error: (-215:Assertion failed).ssize:empty() in function 'cv::resize'

Question

I am receiving this error when running this line of code:

pixels.append( cv2.resize(cv2.imread(raw_folder  + folder +"/" + file),dsize=(128,128)))**

Error:

cv2.error: OpenCV(4.5.2) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-vi271kac\opencv\modules\imgproc\src\resize.cpp:4051: 
error: (-215:Assertion failed) !ssize.empty() in function 'cv::resize'

Answer 1

You may have common problem: when CV2 can't read file then it doesn't raise error but it returns None and now you try to resize None - empty image - and this shows .ssize.empty() .

You should first read image, next check if you get None and next try to resize it.

You should check if raw_folder + folder +"/" + file creates correct path and if you can open it in any other program. Maybe you forgot some / in path (ie. between raw_folder and folder ) or forgot file extension or you create path to not existing file.

path = os.path.join(raw_folder, folder, file)
print('[DEBUG] path:', path)

img = cv2.imread(path)

if img is None:
    print('Wrong path:', path)
else:
    img = cv2.resize(img, dsize=(128,128))
    pixels.append(img)

Answer 2

Another situation that lead to this error was to input an image of the wrong shape. I had an RGB image of shape (3, 540, 960) and got the misleading 'ssize is not empty'. Changing the shape to (540, 960, 3) fixed my problem.