org.openimaj.image.analysis.algorithm.histogram

Class SATWindowedExtractor

java.lang.Object

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

All Implemented Interfaces:

WindowedHistogramExtractor

Direct Known Subclasses:

GradientOrientationHistogramExtractor

public class SATWindowedExtractor
extends Object
implements WindowedHistogramExtractor

This class implements a WindowedHistogramExtractor with the primary purpose of of producing efficient access to histograms of arbitrary windows of the image.

This implementation is based on a stack of SummedAreaTables, with one SummedAreaTable per histogram bin. Obviously this is quite memory intensive, so should probably only be used with small numbers of bins. However, the advantage over a BinnedWindowedExtractor is that the histogram extraction is an O(1) operation, and it is thus very quick for evaluating many windows.

Author:

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

Field Summary

Fields

Modifier and Type	Field and Description
protected int	nbins
protected SummedAreaTable[]	sats

Constructor Summary

Constructors

Modifier	Constructor and Description
	SATWindowedExtractor(FImage[] magnitudeMaps) Construct with the given spatial histogram magnitude maps.
protected	SATWindowedExtractor(int nbins) Protected constructor for subclasses to use if they don't wan't to compute the SATs at construction time

Method Summary

Modifier and Type	Method and Description
Histogram	computeHistogram(int x, int y, int w, int h) Compute the histogram for the given window.
void	computeHistogram(int x, int y, int w, int h, Histogram hist) Compute the histogram for the given window, storing the output in the given Histogram object, which must have the same length as given by WindowedHistogramExtractor.getNumBins().
Histogram	computeHistogram(Rectangle roi) Compute the histogram for the given window.
void	computeHistogram(Rectangle roi, Histogram histogram) Compute the histogram for the given window, storing the output in the given Histogram object, which must have the same length as given by WindowedHistogramExtractor.getNumBins().
protected void	computeSATs(FImage[] magnitudeMaps)
int	getNumBins() Get the number of bins

Methods inherited from class java.lang.Object

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

Field Detail

sats

protected final SummedAreaTable[] sats

nbins

protected final int nbins

Constructor Detail

SATWindowedExtractor

protected SATWindowedExtractor(int nbins)

Protected constructor for subclasses to use if they don't wan't to compute the SATs at construction time

Parameters:

nbins - the number of histogram bins.

SATWindowedExtractor

public SATWindowedExtractor(FImage[] magnitudeMaps)

Construct with the given spatial histogram magnitude maps. Each image represents a bin of the histogram, and each element is the histogram weight at the respective spatial location for the corresponding bin (usually the images will be very sparse).

Parameters:

magnitudeMaps - array of images, one per bin, with each pixel set to the histogram magnitude at that bin

Method Detail

computeSATs

protected void computeSATs(FImage[] magnitudeMaps)

getNumBins

public int getNumBins()

Description copied from interface: WindowedHistogramExtractor

Get the number of bins

Specified by:

getNumBins in interface WindowedHistogramExtractor

Returns:

the number of bins

computeHistogram

public Histogram computeHistogram(Rectangle roi)

Description copied from interface: WindowedHistogramExtractor

Compute the histogram for the given window.

Specified by:

computeHistogram in interface WindowedHistogramExtractor

Parameters:

roi - the window

Returns:

the histogram in the window of the last analysed image

computeHistogram

public Histogram computeHistogram(int x,
                                  int y,
                                  int w,
                                  int h)

Description copied from interface: WindowedHistogramExtractor

Compute the histogram for the given window.

Specified by:

computeHistogram in interface WindowedHistogramExtractor

Parameters:

x - The x-coordinate of the top-left of the window

y - The y-coordinate of the top-left of the window

w - The width of the window

h - The height of the window

Returns:

the histogram in the window of the last analysed image

computeHistogram

public void computeHistogram(int x,
                             int y,
                             int w,
                             int h,
                             Histogram hist)

Description copied from interface: WindowedHistogramExtractor

Compute the histogram for the given window, storing the output in the given Histogram object, which must have the same length as given by WindowedHistogramExtractor.getNumBins().

Specified by:

computeHistogram in interface WindowedHistogramExtractor

Parameters:

x - The x-coordinate of the top-left of the window

y - The y-coordinate of the top-left of the window

w - The width of the window

h - The height of the window

hist - the histogram to write to

computeHistogram

public void computeHistogram(Rectangle roi,
                             Histogram histogram)

Description copied from interface: WindowedHistogramExtractor

Compute the histogram for the given window, storing the output in the given Histogram object, which must have the same length as given by WindowedHistogramExtractor.getNumBins().

Specified by:

computeHistogram in interface WindowedHistogramExtractor

Parameters:

roi - the window

histogram - the histogram to write to