Is there an equivalent of MATLAB's find() in opencv or numpy?

for image processing, i.e to find first/last array of matching pixels.

Answer 1

[Jan]

This is obviously a question for a numpy and opencv forum. But let's see, what an internet search engine finds...

itemindex = numpy.where(array==item)

And perhaps you want Cmp or CmpS in OpenCV, see e.g. http://stackoverflow.com/questions/10597107/opencv-function-similar-to-matlabs-find

Answer 2

[Bill Tubbs]

I wasn't sure about this but you are correct. They both return indexes. I'll share these examples in case they help someone.

>> x = [1 2 3; 2 3 4];
>> find(x==2)

ans =

     2
     3

>> x(find(x==2))

ans =

     2
     2

>> find(x==3)

ans =

     4
     5

Python:

>>> x = np.array([[1, 2, 3], [2, 3, 4]])
>>> np.where(x == 2)
(array([0, 1]), array([1, 0]))
>>> x[np.where(x == 2)]
array([2, 2])
>>> np.where(x == 3)                                                     
(array([0, 1]), array([2, 1]))

Interesting how different indexing is in the two languages!