Python PIL - AttributeError: 'NoneType' object has no attribute 'save'

Question

I use this code to delete the border of an image using PIL:

def RemoveBlackBorders(img):
    bg = Image.new(img.mode, img.size, img.getpixel((0,0)))
    diff = ImageChops.difference(img, bg)
    diff = ImageChops.add(diff, diff, 2.0, -100)
    bbox = diff.getbbox()
    if bbox:
        return img.crop(bbox)

from here

And I use this to process all images contained in a folder:

def CropImages():
    global FOLDER
    for i in range(1, len(os.listdir(FOLDER))+1):
        image = FOLDER + "\\" + str(i) + ".jpg"
        img = Image.open(image)
        img = RemoveBlackBorders(img)
        img.save(image, "JPEG")

Everything works fine and the program does his job. The problem is that if in the folder there is a full black image (which is detected as "border"), the program stuck giving me the error:

 AttributeError: 'NoneType' object has no attribute 'save'

None of the images in the folder get cropped, even if the black image is the last one of the series. Is there a way to skip this image or delete it (which would be better)?

score 3 · Accepted Answer · edited May 23 '17 at 10:26

The Python principle of EAFP could apply here.

Basically you should have your code attempt to execute and then catch an AttributeError, telling it to skip that image.

Like this:

def CropImages():
    global FOLDER
    for i in range(1, len(os.listdir(FOLDER))+1):
        image = FOLDER + "\\" + str(i) + ".jpg"
        img = Image.open(image)
        img = RemoveBlackBorders(img)

        try:
            img.save(image, "JPEG")
        except AttributeError:
            print("Couldn't save image {}".format(image))

This just means that if it finds that error, it'll print the message and then keep looping over the rest.

score 1 · Answer 2 · answered May 19 '15 at 13:46

Since RemoveBlackBorders returns None for images that are 100% border, you can check for None later when deciding whether to save.

def CropImages():
    global FOLDER
    for i in range(1, len(os.listdir(FOLDER))+1):
        image = FOLDER + "\\" + str(i) + ".jpg"
        img = Image.open(image)
        img = RemoveBlackBorders(img)
        if img is not None:
            img.save(image, "JPEG")

Python PIL - AttributeError: 'NoneType' object has no attribute 'save'

2 Answers2