CODEWITHSUNDEEP
pythonnumpy
victor
victor

Reputation: 6768

Fast image coordinate lookup in Numpy

I've got a big numpy array full of coordinates (about 400):

[[102, 234],
 [304, 104],
  ....
]

And a numpy 2d array my_map of size 800x800.

What's the fastest way to look up the coordinates given in that array? I tried things like paletting as described in this post: http://opencvpython.blogspot.com/2012/06/fast-array-manipulation-in-numpy.html but couldn't get it to work.

I was also thinking about turning each coordinate into a linear index of the map and then piping it straight into my_map like so:

my_map[linearized_coords]

but I couldn't get vectorize to properly translate the coordinates into a linear fashion. Any ideas?

Upvotes: 1

Views: 407

Answers (1)

nneonneo
nneonneo

Reputation: 179402

Try using a tuple for indexing:

my_map[tuple(coords.T)]

This selects elements of the array via advanced indexing.

Upvotes: 2

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