CODEWITHSUNDEEP
pythonarraysnumpy
Tim R
Tim R

Reputation: 524

Find X and Y Coordinates of a value in a python array

I am trying to get the x and y coordinates of a given value in a numpy image array.

I can do it by running through the rows and columns manually with a for statement, but this seems rather slow and I am possitive there is a better way to do this.

I was trying to modify a solution I found in this post. Finding the (x,y) indexes of specific (R,G,B) color values from images stored in NumPy ndarrays

a = image
c = intensity_value

y_locs = np.where(np.all(a == c, axis=0))
x_locs = np.where(np.all(a == c, axis=1))

return np.int64(x_locs), np.int64(y_locs)

I have the np.int64 to convert the values back to int64.

I was also looking at numpy.where documentation

Upvotes: 0

Views: 9312

Answers (1)

YXD
YXD

Reputation: 32521

I don't quite understand the problem. The axis parameter in all() runs over the colour channels (axis 2 or -1) rather than the x and y indices. Then where() will give you the coordinates of the matching values in the image:

>>> # set up data
>>> image = np.zeros((5, 4, 3), dtype=np.int)
>>> image[2, 1, :] = [7, 6, 5]
>>> # find indices
>>> np.where(np.all(image == [7, 6, 5], axis=-1))
(array([2]), array([1]))
>>>

This is really just repeating the answer you linked to. But is a bit too long for a comment. Maybe you could explain a bit more why you need to modify the previous answer? It doesn't seem like you do need to.

Upvotes: 1

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