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java.lang.Objecthhreco.recognition.ZernikeFE
Compute Zernike moments of the specified order [1]. This is a global feature of a shape and is independent of stroke-number, -order, and -direction. This feature (specifically the magnitude of the moment) is invariant to rotation, but not invariant to scale and translation. Therefore, it is important to normalize the shape before extracting the moment features. All moment features up to the specified order are returned except for order 0 and 1. This is because for shapes that have been scale- and translation- normalized, these values are the same across all shapes and therefore they are not useful for distinguishing shapes. If desired, one can call zer_mom directly to obtain these moment values.
[1] 'A. Khotanzad and Y.H. Hong' "Invariant image recognition by Zernike Moments", IEEE trans. on Pattern Analysis and Machine Intelligence, vol.12, no.5, pp.489-487, May 1990.
Field Summary | |
static int |
DEFAULT_ORDER
The default order of Zernike moments is set to 8. |
Constructor Summary | |
ZernikeFE()
Create a Zernike feature extractor with the default order. |
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ZernikeFE(int order)
Create a Zernike feature extractor with the specified order. |
Method Summary | |
double[] |
apply(TimedStroke[] s)
Return the magnitudes of the Zernike moments of the default order. |
double[] |
apply(TimedStroke[] s,
int order)
Return the magnitudes of the Zernike moments of the specified order. |
java.lang.String |
getName()
Return the name of this feature extractor. |
int |
getOrder()
Return the moment order. |
void |
setOrder(int order)
Set the moment order (appears as 'n' in the equations [1]) |
static double[] |
zernikeMoments(TimedStroke[] s)
Compute Zernike moments of the stroke. |
static double[] |
zernikeMoments(TimedStroke[] s,
int order)
Compute Zernike moments of the specified order and return the magnitudes of the moments. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public static int DEFAULT_ORDER
Constructor Detail |
public ZernikeFE()
public ZernikeFE(int order)
Method Detail |
public double[] apply(TimedStroke[] s)
apply
in interface FeatureExtractor
public double[] apply(TimedStroke[] s, int order)
public void setOrder(int order)
public int getOrder()
public java.lang.String getName()
getName
in interface FeatureExtractor
public static double[] zernikeMoments(TimedStroke[] s)
public static double[] zernikeMoments(TimedStroke[] s, int order)
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