OpenCV-Python: img is not a numpy array, neither a scalar

Question

I'm trying to write a save image function. The below code is expected to create a copy of the original image as saved-test-image.jpg.

originalImage = "test-image.jpg"
savedImage = cv2.imwrite("saved-test-image.jpg",originalImage)

The execution of the lines gives the follwing back:

Traceback (most recent call last):
  File "UnitTest.py", line 159, in test_save_and_delete_image
    savedImage = cv2.imwrite('unittest-images/saved-test-image.jpg', originalImage)
TypeError: img is not a numpy array, neither a scalar

What needs to be changed here?

Solution

Well opencv is right, you save originalImage, but originalImage is a string (the filename, your first line).

You need to cv2.imread(..) your image into a numpy array first:

originalImage = cv2.imread("test-image.jpg")
savedImage = cv2.imwrite("saved-test-image.jpg",originalImage)

If you simply want to copy an image file however, there is no need to load it into memory, you can simply copy the file, without using opencv:

from shutil import copyfile

originalImage = "test-image.jpg"
copyfile(originalImage,"saved-test-image.jpg")

In this case, it will simply copy the file - regardless what its content is - so even if it is a corrupt image, or not an image at all, it will be copied.