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/**
* Interpolation par Spline Cubique
*
* @author Xavier Philippeau
*
*/
public class Interpolate {
// spline factor in the range [-1,0]
private double a = -0.5;
// original image
private Channel channel = null;
public Interpolate(Channel c) {
this.channel = c;
}
// --- Spline coefficients ----------------------------------------------------
// C0(t) = -at3 + at2
private double C0(double t) {
return -a*t*t*t + a*t*t;
}
// C1(t) = -(a+2)t3 + (2a+3)t2 - at
private double C1(double t) {
return -(a+2)*t*t*t + (2*a+3)*t*t - a*t;
}
// C2(t) = (a+2)t3 - (a+3)t2 + 1
private double C2(double t) {
return (a+2)*t*t*t - (a+3)*t*t + 1;
}
// C3(t) = at3 - 2at2 + at
private double C3(double t) {
return a*t*t*t - 2*a*t*t + a*t;
}
// --- Continous interpolation from discrete values ---------------------------
// discret value for pixel of coordinates: i (integer) , j (integer)
private double f(int i, int j) {
return this.channel.getValue(i, j);
}
// compute interpolated value for pixel of coordinates: x (real) , j (integer)
private double H(int j, double x) {
int i = (int)x;
return f(i-1,j)*C3(x-i) + f(i,j)*C2(x-i) + f(i+1,j)* C1(x-i) + f(i+2,j)*C0(x-i);
}
// compute interpolated value for pixel of coordinates: x (real) , y (real)
public double value(double x, double y) {
int j = (int)y;
return H(j-1,x)*C3(y-j) + H(j,x)*C2(y-j) + H(j+1,x)*C1(y-j) + H(j+2,x)*C0(y-j);
}
} |
[image] Interpolation spline cubique
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