sascha@427: package de.intevation.flys.artifacts.math;
sascha@427: 
sascha@452: import org.apache.log4j.Logger;
sascha@452: 
sascha@427: public class LinearRemap
sascha@427: {
sascha@452:     private static Logger logger = Logger.getLogger(LinearRemap.class);
sascha@452: 
sascha@427:     public static class Segment {
sascha@427: 
sascha@427:         protected Segment next;
sascha@427: 
sascha@427:         protected double from;
sascha@427:         protected double to;
sascha@427: 
sascha@427:         protected double m;
sascha@427:         protected double b;
sascha@427: 
sascha@427:         public Segment() {
sascha@427:         }
sascha@427: 
sascha@427:         public Segment(
sascha@427:             double from, double to, 
sascha@427:             double m,    double b,
sascha@427:             Segment next
sascha@427:         ) {
sascha@427:             this.from = from;
sascha@427:             this.to   = to;
sascha@427:             this.m    = m;
sascha@427:             this.b    = b;
sascha@427:         }
sascha@427: 
sascha@427:         public double eval(double x) {
sascha@427:             return m*x + b;
sascha@427:         }
sascha@427:     } // class Segment
sascha@427: 
sascha@427:     protected Segment head;
sascha@427: 
sascha@427:     public LinearRemap() {
sascha@427:     }
sascha@427: 
sascha@427:     public void add(
sascha@427:         double from, double to,
sascha@427:         double x1,   double y1,
sascha@427:         double x2,   double y2
sascha@427:     ) {
sascha@427:         // y1 = m*x1 + b <=> b = y1 - m*x1
sascha@427:         // y2 = m*x2 + b
sascha@427:         // y2 - y1 = m*(x2 - x1)
sascha@427:         // m = (y2 - y1)/(x2 - x1)
sascha@427: 
sascha@427:         double m, b;
sascha@427: 
sascha@427:         if (x2 == x1) {
sascha@427:             m = 0.0;
sascha@427:             b = 0.5*(y2 + y1);
sascha@427:         }
sascha@427:         else {
sascha@427:             m = (y2 - y1)/(x2 - x1);
sascha@427:             b = y1 - m*x1;
sascha@427:         }
sascha@427: 
sascha@637:         if (from > to) { double t = from; from = to; to = t; }
sascha@637: 
sascha@427:         head = new Segment(from, to, m, b, head);
sascha@452: 
sascha@452:         if (logger.isDebugEnabled()) {
sascha@452:             logger.debug("LinearRemap.add --------- enter");
sascha@452:             logger.debug("  range: [" + from + ", " + to + "]");
sascha@452:             logger.debug("  " + x1 + " -> " + y1 + " (" + head.eval(x1) + ")");
sascha@452:             logger.debug("  " + x2 + " -> " + y2 + " (" + head.eval(x2) + ")");
sascha@452:             logger.debug("LinearRemap.add --------- leave");
sascha@452:         }
sascha@427:     }
sascha@427: 
sascha@427:     public double eval(double pos, double x) {
sascha@427:         Segment current = head;
sascha@427: 
sascha@427:         while (current != null) {
sascha@427: 
sascha@427:             if (pos >= current.from && pos <= current.to) {
sascha@427:                 return current.eval(x);
sascha@427:             }
sascha@427: 
sascha@427:             current = current.next;
sascha@427:         }
sascha@427: 
sascha@427:         return Double.NaN;
sascha@427:     }
sascha@427: }
sascha@427: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :