`skimage.morphology._skeletonize_various_cy:_table_lookup_index`

Signature

def _table_lookup_index ( image )

Return an index into a table per pixel of a binary image

Take the sum of true neighborhood pixel values where the neighborhood looks like this

 1   2   4
 8  16  32
64 128 256

This code could be replaced by a convolution with the kernel

256 128 64
 32  16  8
  4   2  1

but this runs about twice as fast because of inlining and the hardwired kernel.