Documentation>vl_demo_sift_or

# Source code for ``vl_demo_sift_or.m

This file is located in the ``toolbox/demo folder in VLFeat package.

    % VL_DEMO_SIFT_OR  Demonstrates SIFT orientation detection

    I = vl_impattern('wedge') ;
    ur = 1:size(I,2) ;
    vr = 1:size(I,1) ;

    % distribute frames on a grid
    [u,v] = meshgrid(ur(5:10:end-4),vr(5:10:end-4)) ;
    f = [u(:)';v(:)'] ;
    K = size(f,2) ;
    f = [f ; 4 * ones(1,K) ; 0 * ones(1,K)] ;

    % detect orienntations
    f = vl_sift(single(I), 'frames', f, 'orientations') ;

    figure(1) ; clf ;
    imagesc(single(I)) ; colormap gray ; hold on ;
    vl_plotframe(f,'color','k','linewidth',3) ;
    vl_plotframe(f,'color','y','linewidth',2) ;
    axis equal ; axis off ;
    vl_demo_print('sift_or') ;