/*
* Geotoolkit.org - An Open Source Java GIS Toolkit
* http://www.geotoolkit.org
*
* (C) 2012, Geomatys
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotoolkit.image.interpolation;
import org.geotoolkit.image.iterator.PixelIterator;
/**
* <p>This interpolator may produce somewhat sharper results than classic
* classic BiCubic Interpolation, but that result is image dependent.<br/>
* It's a consequence from increase of biCubic curve amplitude.<br/>
* It use the parameter 'a' recommended by Keys.<br/>
* (Reference: Digital Image Warping, George Wolberg, 1990, pp 129-131, IEEE Computer Society Press, ISBN 0-8186-8944-7)</p>
*
* @author Rémi Marechal (Geomatys).
*/
public class BiCubicInterpolation2 extends BiCubicInterpolation {
/**
* <p>Parameter use in "cubic convolution" computing.<br/>
* a equal -0.5 for classic biCubic interpolation.<br/>
* a equal -1.0 for more amplitude between interpolation results.</p>
*
* @see #getConvolutionValue(double) .
*/
private final double a = -1.0;
/**
* {@inheritDoc }.
*/
public BiCubicInterpolation2(PixelIterator pixelIterator, ResampleBorderComportement rbc, double[] fillValue) {
super(pixelIterator, rbc, fillValue);
}
/**
* {@inheritDoc }.
*/
public BiCubicInterpolation2(PixelIterator pixelIterator) {
super(pixelIterator);
}
/**
* Compute coefficient apply on current pixel value.
* Compute value of Kernel filter.
*
* @param t difference between interpolation position and pixel position.
* t >= 0 && t<2.
* @return Kernel filter value.
*/
private double getConvolutionValue(double t) {
final double tAbs = Math.abs(t);
if (tAbs <= 1) {
return ((a+2)*tAbs - (a+3))*tAbs*tAbs + 1;//(a + 2)|x|^3 - (a + 3)|x|^2 + 1
} else if(tAbs >1 && tAbs < 2) {
return (((tAbs - 5)*tAbs + 8)*tAbs - 4)*a;// a|x|^3 - 5a|x|^2 + 8a|x| - 4a
} else {
return 0;
}
}
/**
* {@inheritDoc }
*
* Cubic interpolation from 4 values.<br/>
* With always t0 <= t<= t0 + 3 <br/>
* <p>For example : cubic interpolation between 4 pixels.<br/>
*
*
* t = 0 1 2 3<br/>
* f(t) = |f0|f1|f2|f3|<br/>
* In this example t0 = 0.<br/><br/>
*
* Another example :<br/>
* t = -5 -4 -3 -2<br/>
* f(t) = |f0|f1|f2|f3|<br/>
* In this example parameter t0 = -5.</p>
*
* @param t0 f(t0) = f[0].Current position from first pixel interpolation.
* @param t position of interpolation.
* @param f pixel values from t = {0, 1, 2, 3}.
* @return cubic interpolation at t position.
*/
@Override
protected double interpolate1D(double t0, double t, double... f) {
assert (f.length == 4) : "impossible to interpolate with less or more than 4 values";
double res = 0;
int compteur = 0;
for (double ft : f) {
res += getConvolutionValue(t-t0 - compteur++)*ft;
}
return checkValue(res);
}
}