Patch descriptor based on histogrammed filter responses. Creates a descriptor for an image that is fairly robust to small perturbations of the image. This differs from descimg_GRAD because instead of histograming over the smoothed gradient, which is essentially over the output of derivative of gaussian filters, the filter bank can be specified. Factor slowdown from descimg_GRAD depends on size and number of filters. INPUTS I - MxNxT double array (cuboid) with most vals in range [-1,1] FB - 2D filter bank [see above] ch2params - see imagedesc_ch2desc OUTPUTS desc - 1xp feature vector See also IMAGEDESC, DESCPATCH_GRAD, IMAGEDESC_CH2DESC