org.openimaj.image.analysis.algorithm.histogram

Class GradientOrientationHistogramExtractor

java.lang.Object

org.openimaj.image.analysis.algorithm.histogram.SATWindowedExtractor

org.openimaj.image.analysis.algorithm.histogram.GradientOrientationHistogramExtractor

All Implemented Interfaces:

ImageAnalyser<FImage>, WindowedHistogramExtractor

public class GradientOrientationHistogramExtractor
extends SATWindowedExtractor
implements ImageAnalyser<FImage>

Implementation of the WindowedHistogramExtractor for efficiently extracting gradient orientation histograms. This implementation is built on top of a SATWindowedExtractor. The analyseImage(FImage) method can be used to precompute the underlying data required for efficient histogram extraction using any of the computeHistogram methods.

Computed histograms are simply the sum of magnitudes for each orientation bin over the given window. If you need to generate more complex features (for example, aggregated spatially binned histograms) then use this class in combination with a SpatialBinningStrategy.

The analyseImage(FImage, FImage) method can be used to construct histograms with moderated magnitudes (for example, suppressing all magnitudes except those at edges).

Author:

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

Field Summary

Fields inherited from class org.openimaj.image.analysis.algorithm.histogram.SATWindowedExtractor

nbins, sats

Constructor Summary

Constructors

Constructor and Description
GradientOrientationHistogramExtractor(int nbins, boolean histogramInterpolation, FImageGradients.Mode orientationMode) Construct a new GradientOrientationHistogramExtractor with the given number of bins.

Method Summary

Modifier and Type	Method and Description
void	analyseImage(FImage image) Analyse an image.
void	analyseImage(FImage image, FImage edges) Analyse the given image, but construct the internal data such that the gradient magnitudes are multiplied by the given edge map before being accumulated.

Methods inherited from class org.openimaj.image.analysis.algorithm.histogram.SATWindowedExtractor

computeHistogram, computeHistogram, computeHistogram, computeHistogram, computeSATs, getNumBins

Methods inherited from class java.lang.Object

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

Constructor Detail

GradientOrientationHistogramExtractor

public GradientOrientationHistogramExtractor(int nbins,
                                             boolean histogramInterpolation,
                                             FImageGradients.Mode orientationMode)

Construct a new GradientOrientationHistogramExtractor with the given number of bins. Optionally perform linear interpolation across orientation bins. Histograms can also use either signed or unsigned gradients.

Parameters:

nbins - number of bins

histogramInterpolation - if true cyclic linear interpolation is used to share the magnitude across the two closest bins; if false only the closest bin will be filled.

orientationMode - the range of orientations to extract

Method Detail

analyseImage

public void analyseImage(FImage image)

Description copied from interface: ImageAnalyser

Analyse an image.

Specified by:

analyseImage in interface ImageAnalyser<FImage>

Parameters:

image - The image to process in place.

analyseImage

public void analyseImage(FImage image,
                         FImage edges)

Analyse the given image, but construct the internal data such that the gradient magnitudes are multiplied by the given edge map before being accumulated. This could be used to suppress all magnitudes except those at edges; the resultant extracted histograms would only contain information about edge gradients.

Parameters:

image - the image to analyse

edges - the edge image