faster filtering with matched spatial filters to dot speed

README.md

@@ -5,6 +5,7 @@ Implements motion energy filtering as described in Adelson & Bergen (1985), on 3
 See also these excellent tutorials on the 2D equivalent of these filters
 * http://www.georgemather.com/Model.html (George Mather)
 * http://mplab.ucsd.edu/~marni/CSHL_Tutorials/MotionEnergy.tar (Simoncelli, Glimcher, Chichilnisky)
+* http://www.cns.nyu.edu/~david/courses/perceptionGrad/syllabus2015.html (David Heeger)
 
 INPUT
 - stimulus, a 3d matrix containing the x-y-t stimulus movie
@@ -23,7 +24,7 @@ OUTPUT
 filters (optional)
 
 Anne Urai, 2016
-
 [email protected] / anneurai.net
+Thanks to Klaus Wimmer
 
-[![DOI](https://zenodo.org/badge/doi/10.5281/zenodo.45139.svg)](http://dx.doi.org/10.5281/zenodo.45139)
+[![DOI](https://zenodo.org/badge/doi/10.5281/zenodo.45139.svg)](http://dx.doi.org/10.5281/zenodo.45139)

applyFilters.m

@@ -0,0 +1,67 @@
+% Permission is hereby granted, free of charge, to any person obtaining a 
+% copy of this software and associated documentation files (the "Software"), 
+% to deal in the Software without restriction, including without limitation 
+% the rights to use, copy, modify, merge, publish, distribute, sublicense, 
+% and/or sell copies of the Software, and to permit persons to whom the 
+% Software is furnished to do so, subject to the following conditions:
+% 
+% The above copyright notice and this permission notice shall be included 
+% in all copies or substantial portions of the Software.
+% If you use the Software for your own research, cite the paper.
+% 
+% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
+% OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
+% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
+% DEALINGS IN THE SOFTWARE.
+%
+% Anne Urai and Klaus Wimmer, 2016
+% [email protected] / [email protected]
+
+function energy = applyFilters(stim, f1, f2, g1, g2)
+% apply filtering according to Adelson & Bergen figure 18b
+% composite filters!
+tic;
+stimsize = size(stim, 1);
+nFrames  = size(stim, 3);
+
+% spatial filtering
+A0 = zeros(stimsize, stimsize, nFrames);
+B0 = zeros(stimsize, stimsize, nFrames);
+for f = 1:nFrames,
+    A0(:,:,f) = conv2(stim(:,:,f), f1, 'same');
+    B0(:,:,f) = conv2(stim(:,:,f), f2, 'same');
+end
+
+% temporal filtering
+A0_     = reshape(A0, stimsize * stimsize, []);
+B0_     = reshape(B0, stimsize * stimsize, []);
+
+A1_     = filter(g1, 1, A0_, [], 2);
+A1      = reshape(A1_, stimsize, stimsize, []);
+
+A2_     = filter(g2, 1, A0_, [], 2);
+A2      = reshape(A2_, stimsize, stimsize, []);
+
+B1_     = filter(g1, 1, B0_, [], 2);
+B1      = reshape(B1_, stimsize, stimsize, []);
+
+B2_     = filter(g2, 1, B0_, [], 2);
+B2      = reshape(B2_, stimsize, stimsize, []);
+
+% Adelson and Bergen, fig 18b
+% opponentenergy    = 4*(A1 .* B2 - A2 .* B1); % this is the opponent energy
+% energy_left       = (A1-B2).^2 + (A2+B1).^2;
+% energy_right      = (A1+B2).^2 + (A2-B1).^2;
+% energy_opponent   = energy_right - energy_left; % opponent energy
+
+energy              = A1 .* B2 - A2 .* B1;
+
+% energy_static     = A1.^2 + A2.^2 + B1.^2 + B2.^2;
+% velocity          = energy_opponent ./ energy_static;
+% assert(~any(isnan(velocity)));
+toc;
+
+end