package org.jcodec.scale;

import org.jcodec.common.model.Size;

public class LanczosResampler extends BaseResampler {
  private static final int _nTaps = 6;
  
  private int precision = 256;
  
  private short[][] tapsXs;
  
  private short[][] tapsYs;
  
  private double _scaleFactorX;
  
  private double _scaleFactorY;
  
  public LanczosResampler(Size from, Size to) {
    super(from, to);
    this._scaleFactorX = (double)to.getWidth() / (double)from.getWidth();
    this._scaleFactorY = (double)to.getHeight() / (double)from.getHeight();
    this.tapsXs = new short[this.precision][6];
    this.tapsYs = new short[this.precision][6];
    buildTaps(6, this.precision, this._scaleFactorX, this.tapsXs);
    buildTaps(6, this.precision, this._scaleFactorY, this.tapsYs);
  }
  
  private static double sinc(double x) {
    return (x == 0.0D) ? 1.0D : (Math.sin(x) / x);
  }
  
  private static void buildTaps(int nTaps, int precision, double scaleFactor, short[][] tapsOut) {
    double[] taps = new double[nTaps];
    for (int i = 0; i < precision; i++) {
      double o = (double)i / (double)precision;
      for (int j = -nTaps / 2 + 1, t = 0; j < nTaps / 2 + 1; j++, t++) {
        double x = -o + (double)j;
        double sinc_val = scaleFactor * sinc(scaleFactor * x * Math.PI);
        double wnd_val = Math.sin(x * Math.PI / (double)(nTaps - 1) + 1.5707963267948966D);
        taps[t] = sinc_val * wnd_val;
      } 
      normalizeAndGenerateFixedPrecision(taps, 7, tapsOut[i]);
    } 
  }
  
  protected short[] getTapsX(int dstX) {
    int oi = (int)((double)(float)(dstX * this.precision) / this._scaleFactorX);
    int sub_pel = oi % this.precision;
    return this.tapsXs[sub_pel];
  }
  
  protected short[] getTapsY(int dstY) {
    int oy = (int)((double)(float)(dstY * this.precision) / this._scaleFactorY);
    int sub_pel = oy % this.precision;
    return this.tapsYs[sub_pel];
  }
  
  protected int nTaps() {
    return 6;
  }
}