boofcv.alg.feature.describe

Class DescribeSiftCommon

java.lang.Object

boofcv.alg.feature.describe.DescribeSiftCommon

Direct Known Subclasses:

DescribeDenseSiftAlg, DescribePointSift

public class DescribeSiftCommon
extends java.lang.Object

Base class for SIFT descriptors. Provides common functionality between sparse and dense computations.

Constructor Summary

Constructors

Constructor and Description
DescribeSiftCommon(int widthSubregion, int widthGrid, int numHistogramBins, double weightingSigmaFraction, double maxDescriptorElementValue) Configures the descriptor.

Method Summary

Modifier and Type	Method and Description
int	getCanonicalRadius() Radius of descriptor in pixels.
int	getDescriptorLength() Number of elements in the descriptor.
static void	normalizeDescriptor(TupleDesc_F64 descriptor, double maxDescriptorElementValue) Adjusts the descriptor.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DescribeSiftCommon

public DescribeSiftCommon(int widthSubregion,
                          int widthGrid,
                          int numHistogramBins,
                          double weightingSigmaFraction,
                          double maxDescriptorElementValue)

Configures the descriptor.

Parameters:

widthSubregion - Width of sub-region in samples. Try 4

widthGrid - Width of grid in subregions. Try 4.

numHistogramBins - Number of bins in histogram. Try 8

weightingSigmaFraction - Sigma for Gaussian weighting function is set to this value * region width. Try 0.5

maxDescriptorElementValue - Helps with non-affine changes in lighting. See paper. Try 0.2

Method Detail

normalizeDescriptor

public static void normalizeDescriptor(TupleDesc_F64 descriptor,
                                       double maxDescriptorElementValue)

Adjusts the descriptor. This adds lighting invariance and reduces the affects of none-affine changes in lighting. 1) Apply L2 normalization 2) Clip using max descriptor value 3) Apply L2 normalization again

getDescriptorLength

public int getDescriptorLength()

Number of elements in the descriptor.

getCanonicalRadius

public int getCanonicalRadius()

Radius of descriptor in pixels. Width is radius*2