Using opencv / Numpy to find white pixels in a color image using python

Question

I have an image I loaded using opencv, that I would like to find pixels that are white.

input_img = [[[255,255,255], [0,127,255]],
             [[255,255,255], [255,127,255]]]

should return

white = [[1, 0],
         [1, 0]]

Is there a way to do this without reshaping or without an expensive for loop? Using something like numpy.where?

Are you looking for pure white or pixels that looks close to white? Because of noise in images, some of the pixels will not be exactly, (255, 255, 255). Perhaps post a sample test image if that is convenient. — lightalchemist
– lightalchemist, Commented Mar 14, 2014 at 7:26
These are white pixels - the image I receive already has noise removed (or at least I can assume that it has). — Charles L.
– Charles L., Commented Mar 15, 2014 at 3:32

YXD · Accepted Answer · 2014-03-15 16:40:31Z

5

How about

(input_img == 255).all(axis=2)

edited Mar 15, 2014 at 16:40

answered Mar 14, 2014 at 8:03

YXD

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Comments

vehsakul · Accepted Answer · 2014-03-14 05:59:27Z

3

This should do it

input_img = [[[255,255,255], [0,127,255]],
         [[255,255,255], [255,127,255]]]
white = np.array(np.sum(input_img, axis=-1) == 765, dtype=np.int32)

edited Mar 14, 2014 at 5:59

answered Mar 14, 2014 at 5:53

vehsakul

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1 Comment

Jorge Y. C. Rodriguez Over a year ago

maybe i got it wrong, but how come this returns this (array([0, 1]), array([0, 0]))

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