package org.jcodec.scale;

import org.jcodec.common.model.Size;

public class BicubicResampler extends BaseResampler {
  private short[][] horizontalTaps;
  
  private short[][] verticalTaps;
  
  private static double alpha = 0.6D;
  
  public BicubicResampler(Size from, Size to) {
    super(from, to);
    this.horizontalTaps = buildFilterTaps(to.getWidth(), from.getWidth());
    this.verticalTaps = buildFilterTaps(to.getHeight(), from.getHeight());
  }
  
  private static short[][] buildFilterTaps(int to, int from) {
    double[] taps = new double[4];
    short[][] tapsOut = new short[to][4];
    double ratio = (double)from / (double)to;
    double toByFrom = (double)to / (double)from;
    double srcPos = 0.0D;
    for (int i = 0; i < to; i++) {
      double fraction = srcPos - (double)(int)srcPos;
      for (int t = -1; t < 3; t++) {
        double d = (double)t - fraction;
        if (to < from)
          d *= toByFrom; 
        double x = Math.abs(d);
        double xx = x * x;
        double xxx = xx * x;
        if (d >= -1.0D && d <= 1.0D) {
          taps[t + 1] = (2.0D - alpha) * xxx + (-3.0D + alpha) * xx + 1.0D;
        } else if (d < -2.0D || d > 2.0D) {
          taps[t + 1] = 0.0D;
        } else {
          taps[t + 1] = -alpha * xxx + 5.0D * alpha * xx - 8.0D * alpha * x + 4.0D * alpha;
        } 
      } 
      normalizeAndGenerateFixedPrecision(taps, 7, tapsOut[i]);
      srcPos += ratio;
    } 
    return tapsOut;
  }
  
  protected short[] getTapsX(int dstX) {
    return this.horizontalTaps[dstX];
  }
  
  protected short[] getTapsY(int dstY) {
    return this.verticalTaps[dstY];
  }
  
  protected int nTaps() {
    return 4;
  }
}