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

You can get the alpha data out of whole image in one go by converting image to string with 'A' mode e.g this example get alpha data out of image and saves it as grey scale image :)

from PIL import Image

imFile="white-arrow.png"
im = Image.open(imFile, 'r')
print im.mode == 'RGBA'

rgbData = im.tostring("raw", "RGB")
print len(rgbData)
alphaData = im.tostring("raw", "A")
print len(alphaData)

alphaImage = Image.fromstring("L", im.size, alphaData)
alphaImage.save(imFile+".alpha.png")