How to check whether a jpeg image is color or gray scale using only Python stdlib

Question

I have to write a test case in python to check whether a jpg image is in color or grayscale. Can anyone please let me know if there is any way to do it with out installing e

Answer 1

In case of a grayscale image, all channels in a certain pixel are equal (if you only have one channel then you don't have a problem) . So basicly if you list all the pixels with their 3 channels values, you suppose to see that each pixel has all 3 channels equal.

Image.getcolors() returns an unsorted list of (count, pixel) values.

im = Image.open('path_to_image.whatever')
color_count = im.getcolors()

If len(color_count) exceeds 256, this method returns None - meaning that you had more than 256 color-options in your pixel list, hence it is a colored image (in case of grayscale you can only have 256 colors (0,0,0) to (255,255,255)). So after that you only need :

if color_count: 
    # your image is grayscale
else:
    # your images is colored

Notice this will work only when using the default parameter value of getcolors().

Documentation: https://pillow.readthedocs.io/en/3.0.x/reference/Image.html#PIL.Image.Image.getcolors