sascha@361: package de.intevation.gnv.math;
sascha@361: 
sascha@361: import java.util.List;
sascha@361: import java.util.Collections;
sascha@361: 
sascha@361: import com.vividsolutions.jts.geom.Coordinate;
sascha@361: import com.vividsolutions.jts.geom.Envelope;
sascha@361: 
sascha@361: import com.vividsolutions.jts.index.quadtree.Quadtree;
sascha@361: 
sascha@361: /**
sascha@361:  *  @author Sascha L. Teichmann
sascha@361:  */
sascha@361: public final class Interpolation2D
sascha@361: {
sascha@361:     public interface Consumer {
sascha@361:         void interpolated(Coordinate point);
sascha@361:     } // interface Consumer
sascha@361: 
sascha@361:     private Interpolation2D() {
sascha@361:     }
sascha@361: 
sascha@361:     public static void interpolate(
sascha@361:         List<? extends Coordinate> path,
sascha@361:         List<? extends Point2d>    points,
sascha@361:         double                     from,
sascha@361:         double                     to,
sascha@361:         int                        steps,
sascha@361:         Metrics                    metrics,
sascha@361:         Consumer                   consumer
sascha@361:     ) {
sascha@361:         int N = path.size();
sascha@361:         int M = points.size();
sascha@361: 
sascha@361:         if (M < 1 || N < 2) { // nothing to do
sascha@361:             return;
sascha@361:         }
sascha@361:         // figure out max delta(p[i].x, p[i-1].x) 
sascha@361:         Collections.sort(points, Point2d.X_COMPARATOR);
sascha@361:         double dxMax = -Double.MAX_VALUE;
sascha@361:         for (int i = 1; i < M; ++i) {
sascha@361:             double dx = Math.abs(path.get(i).x - path.get(i-1).x);
sascha@361:             if (dx > dxMax) {
sascha@361:                 dxMax = dx;
sascha@361:             }
sascha@361:         }
sascha@361: 
sascha@361:         dxMax = dxMax*0.5d + 1e-5d;
sascha@361: 
sascha@361:         // figure out max delta(p[i].y, p[i-1].y) 
sascha@361:         Collections.sort(path, Point2d.X_COMPARATOR);
sascha@361:         double dyMax = -Double.MAX_VALUE;
sascha@361:         for (int i = 1; i < M; ++i) {
sascha@361:             double dy = Math.abs(path.get(i).y - path.get(i-1).y);
sascha@361:             if (dy > dyMax) {
sascha@361:                 dyMax = dy;
sascha@361:             }
sascha@361:         }
sascha@361: 
sascha@361:         dyMax = dyMax*0.5d + 1e-5d;
sascha@361: 
sascha@361:         // put into spatial index to speed up finding neighbors.
sascha@361:         Quadtree spatialIndex = new Quadtree();
sascha@361: 
sascha@361:         for (int i = 0; i < M; ++i) {
sascha@361:             Point2d p = points.get(i);
sascha@361:             spatialIndex.insert(p.envelope(), p);
sascha@361:         }
sascha@361: 
sascha@361:         LinearToMap linearToMap = new LinearToMap(
sascha@361:             path, from, to, metrics);
sascha@361: 
sascha@361:         double dP = (to - from)/steps;
sascha@361: 
sascha@361:         Coordinate center = new Coordinate();
sascha@361: 
sascha@361:         Envelope queryBuffer = new Envelope();
sascha@361: 
sascha@361:         Point2d [] neighbors = new Point2d[4];
sascha@361: 
sascha@361:         for (double p = to; p <= from; p += dP) {
sascha@361:             if (!linearToMap.locate(p, center)) {
sascha@361:                 continue;
sascha@361:             }
sascha@361:             queryBuffer.init(
sascha@361:                 center.x - dxMax, center.x + dxMax, 
sascha@361:                 center.y - dyMax, center.y + dyMax);
sascha@361: 
sascha@361:             List potential = spatialIndex.query(queryBuffer);
sascha@361: 
sascha@361:             L1Comparator invL1 = new L1Comparator(center);
sascha@361:             Collections.sort(potential, invL1);
sascha@361: 
sascha@361:             neighbors[0] = neighbors[1] = 
sascha@361:             neighbors[2] = neighbors[3] = null;
sascha@361: 
sascha@361:             /* bit code of neighbors
sascha@361:                0---1
sascha@361:                | x |
sascha@361:                2---3
sascha@361:             */
sascha@361: 
sascha@361:             int mask = 0;
sascha@361:             // reversed order is essential here!
sascha@361:             for (int i = potential.size()-1; i >= 0; --i) {
sascha@361:                 Point2d n = (Point2d)potential.get(i);
sascha@361:                 int code = n.x > center.x ? 1 : 0;
sascha@361:                 if (n.y > center.y) code |= 2;
sascha@361:                 neighbors[code] = n;
sascha@361:                 mask |= 1 << code;
sascha@361:             }
sascha@361: 
sascha@361:             int numNeighbors = Integer.bitCount(mask);
sascha@361: 
sascha@361:             // only interpolate if we have all four neighbors
sascha@361:             // and we do not have any gaps.
sascha@361:             if (numNeighbors == 4
sascha@361:             && !neighbors[0].hasIGap(neighbors[0])
sascha@361:             && !neighbors[1].hasJGap(neighbors[3])
sascha@361:             && !neighbors[3].hasIGap(neighbors[2])
sascha@361:             && !neighbors[2].hasJGap(neighbors[0])
sascha@361:             ) {
sascha@361:                 double z1 = interpolate(
sascha@361:                     neighbors[0].x, neighbors[0].z,
sascha@361:                     neighbors[1].x, neighbors[1].z,
sascha@361:                     center.x);
sascha@361:                 double z2 = interpolate(
sascha@361:                     neighbors[2].x, neighbors[2].z,
sascha@361:                     neighbors[3].x, neighbors[3].z,
sascha@361:                     center.x);
sascha@361:                 double y1 = interpolate(
sascha@361:                     neighbors[0].x, neighbors[0].y,
sascha@361:                     neighbors[1].x, neighbors[1].y,
sascha@361:                     center.x);
sascha@361:                 double y2 = interpolate(
sascha@361:                     neighbors[2].x, neighbors[2].y,
sascha@361:                     neighbors[3].x, neighbors[3].y,
sascha@361:                     center.x);
sascha@361:                 center.z = interpolate(
sascha@361:                     y1, z1,
sascha@361:                     y2, z2,
sascha@361:                     center.y);
sascha@361:                 consumer.interpolated(center);
sascha@361:             }
sascha@361:         }
sascha@361:     }
sascha@361: 
sascha@361:     public static final double interpolate(
sascha@361:         double x1, double y1,
sascha@361:         double x2, double y2,
sascha@361:         double x
sascha@361:     ) {
sascha@361:         if (x2 == x1) {
sascha@361:             return (y1 + y2)*0.5d;
sascha@361:         }
sascha@361:         double m = (y2-y1)/(x2-x1);
sascha@361:         double b = y1 - m*x1;
sascha@361:         return m*x + b;
sascha@361:     }
sascha@361: }
sascha@361: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8: