Compute numerical gradients along x and y directions.
For 2D arrays identical to Matlab's gradient() with a spacing value of
h=1 but ~10-20x faster (due to mexed implementation). Like gradient(),
computes centered derivatives in interior of image and uncentered
derivatives along boundaries. For 3D arrays computes x and y gradient
separately for each channel and concatenates the results.
This code requires SSE2 to compile and run (most modern Intel and AMD
processors support SSE2). Please see: http://en.wikipedia.org/wiki/SSE2.
USAGE
[Gx,Gy] = gradient2( I )
INPUTS
I - [hxwxk] input k channel single image
OUTPUTS
Gx - [hxwxk] x-gradient (horizontal)
Gy - [hxwxk] y-gradient (vertical)
EXAMPLE
I=single(imread('peppers.png'))/255;
tic, [Gx1,Gy1]=gradient(I,1); toc
tic, [Gx2,Gy2]=gradient2(I); toc
isequal(Gx1,Gx2), isequal(Gy1,Gy2)
See also gradient, gradientMag
Piotr's Computer Vision Matlab Toolbox Version 3.00
Copyright 2014 Piotr Dollar & Ron Appel. [pdollar-at-gmail.com]
Licensed under the Simplified BSD License [see external/bsd.txt]