Documentation>C API
Local Intensity Order Pattern (LIOP) descriptor
Hana Sarbortova
Andrea Vedaldi

liop.h implements Local Intensity Order Pattern descriptor (LIOP) of [32] . LIOP is a local image descriptor, similarly to the SIFT descriptor.

Getting started with LIOP demonstrates how to use the C API to compute the LIOP descriptor of a patch. For further details refer to:

Getting started with LIOP

The following code fragment demonstrates how tow to use liop.h in a C program in order to compute the LIOP descriptor of an image patch.

#include <vl/liop.h>
// Create a new object instance (these numbers corresponds to parameter
// values proposed by authors of the paper, except for 41)
vl_size sideLength = 41 ;
VlLiopDesc * liop = vl_liopdesc_new_basic (sideLength);
// allocate the descriptor array
float * desc = vl_malloc(sizeof(float) * dimension) ;
// compute descriptor from a patch (an array of length sideLegnth *
// sideLength)
vl_liopdesc_process(liop, desc, patch) ;
// delete the object

The image patch must be of odd side length and in single precision. There are several parameters affecting the LIOP descriptor. An example is the threshold used to discard low-contrast oder pattern in the computation of the statistics. This is changed by using vl_liopdesc_set_intensity_threshold.