Finding coordinates in a picture
Posted on Sun 01 December 2013 in Notes
This is a very handy one liner I found in Programming Computer Vision, that can give you the coordinates of non-black pixels in an image.
In [25]: a = np.random.randint(10, size =(5,5))
In [26]: a[a>6] = 0
In [27]: a
Out[27]:
array([[8, 0, 0, 0, 6],
[0, 6, 8, 0, 0],
[9, 0, 0, 6, 6],
[0, 0, 0, 8, 0],
[0, 0, 0, 0, 0]])
In [28]: coord = np.array(a.nonzero()).T
In [29]: coord
Out[29]:
array([[0, 0],
[0, 4],
[1, 1],
[1, 2],
[2, 0],
[2, 3],
[2, 4],
[3, 3]])
It's the np.array(a.nonzero()).T where the magic happens.