How to get alpha value of a PNG image with PIL?

Question

How to detect if a PNG image has transparent alpha channel or not using PIL?

img = Image.open(\'example.png\', \'r\')
has_alpha = img.mode == \'RGBA\'
         


        

Answer 1

# python 2.6+

import operator, itertools

def get_alpha_channel(image):
    "Return the alpha channel as a sequence of values"

    # first, which band is the alpha channel?
    try:
        alpha_index= image.getbands().index('A')
    except ValueError:
        return None # no alpha channel, presumably

    alpha_getter= operator.itemgetter(alpha_index)
    return itertools.imap(alpha_getter, image.getdata())