org.openimaj.image.feature.local.detector.ipd.extractor

Class InterestPointGradientFeatureExtractor

java.lang.Object

org.openimaj.image.feature.local.detector.ipd.extractor.InterestPointGradientFeatureExtractor

All Implemented Interfaces:

FeatureVectorExtractor<OrientedFeatureVector,InterestPointImageExtractorProperties<Float,FImage>>

public class InterestPointGradientFeatureExtractor
extends Object
implements FeatureVectorExtractor<OrientedFeatureVector,InterestPointImageExtractorProperties<Float,FImage>>

Class capable of extracting local descriptors from an interest point InterestPointData from an interest point detector InterestPointDetector. The actual feature extracted is determined by the GradientFeatureProvider that is provided by the GradientFeatureProviderFactory set during construction.

The GradientFeatureExtractor first calculates the dominant orientation of the image patch described by the InterestPointImageExtractorProperties and then iterates over the pixels in an oriented square, centered on the interest point, passing the gradient and magnitude values of the respective pixel to the GradientFeatureProvider.

The size of the sampling square is exactly equal to the patch in the properties, this is in turn controlled by the interest point's scale and possibly its shape. For some types of feature provider, this number might need to be set based on the internal settings of the provider.

Author:

Jonathon Hare (jsh2@ecs.soton.ac.uk)

Constructor Summary

Constructors

Constructor and Description
InterestPointGradientFeatureExtractor(AbstractDominantOrientationExtractor dominantOrientationExtractor, GradientFeatureProviderFactory factory)

Method Summary

Modifier and Type	Method and Description
protected OrientedFeatureVector	createFeature(InterestPointImageExtractorProperties<Float,FImage> properties, float orientation)
OrientedFeatureVector[]	extractFeature(InterestPointImageExtractorProperties<Float,FImage> properties) Extract FeatureVector(s), possibly using the information given in the properties.
GradientScaleSpaceImageExtractorProperties<FImage>	getCurrentGradientProps(ScaleSpaceImageExtractorProperties<FImage> properties) Get the GradientScaleSpaceImageExtractorProperties for the given properties.

Methods inherited from class java.lang.Object

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

Constructor Detail

InterestPointGradientFeatureExtractor

public InterestPointGradientFeatureExtractor(AbstractDominantOrientationExtractor dominantOrientationExtractor,
                                             GradientFeatureProviderFactory factory)

Parameters:

dominantOrientationExtractor - how dominant orientations are located

factory - object used to construct GradientFeatureProvider instances which in turn construction the actual features

Method Detail

getCurrentGradientProps

public GradientScaleSpaceImageExtractorProperties<FImage> getCurrentGradientProps(ScaleSpaceImageExtractorProperties<FImage> properties)

Get the GradientScaleSpaceImageExtractorProperties for the given properties. The returned properties are the same as the input properties, but with the gradient images added. For efficiency, this method always returns the same cached GradientScaleSpaceImageExtractorProperties, and internally updates this as necessary. The gradient images are only recalculated when the input image from the input properties is different to the cached one.

Parameters:

properties - input properties

Returns:

cached GradientScaleSpaceImageExtractorProperties

extractFeature

public OrientedFeatureVector[] extractFeature(InterestPointImageExtractorProperties<Float,FImage> properties)

Description copied from interface: FeatureVectorExtractor

Extract FeatureVector(s), possibly using the information given in the properties.

Specified by:

extractFeature in interface FeatureVectorExtractor<OrientedFeatureVector,InterestPointImageExtractorProperties<Float,FImage>>

Parameters:

properties - Properties describing how the features should be extracted.

Returns:

An array of feature vectors.

createFeature

protected OrientedFeatureVector createFeature(InterestPointImageExtractorProperties<Float,FImage> properties,
                                              float orientation)