Table of Contents
This tutorial shows how to extract Local
Intensity Order Pattern (LIOP) deascriptors using VLFeat. LIOP is
implemented in the vl_liop as well as
in vl_covdet.
LIOP descriptor computation
A LIOP descriptor can be computed from a square, gray scale image
with and odd side length patch. This is usually not a
restriction since local patches are obtained by cropping and warpinig
an input image. The descriptor is computed using
the vl_liop function:
descr = vl_covdet(patch) ;
You can use the verbose option verbose if you wish to
see the parametr and descriptor details.
descr = vl_covdet(patch,'Verbose') ;
patch can be a 3D array, with one image per 2D
layer. In this case, descr is a matrix with as many
columns as images. LIOP is also integrated
into vl_covdet.
vl_liop allows full customization of the LIOP
descriptor parameters. These are
discussed here. A parameter that
is commonly tweaked is the intensity threshold to downweight
unstalbe intensity order patterns in the descriptor computation. For
example
descr = vl_covdet(patch,'IntensityThreshold', 0.1) ;
set this threshold to 0.1.