diff options
Diffstat (limited to 'src/main/java/com/kitfox/svg/animation/Bezier.java')
| -rw-r--r-- | src/main/java/com/kitfox/svg/animation/Bezier.java | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/src/main/java/com/kitfox/svg/animation/Bezier.java b/src/main/java/com/kitfox/svg/animation/Bezier.java new file mode 100644 index 0000000..1fae8c1 --- /dev/null +++ b/src/main/java/com/kitfox/svg/animation/Bezier.java @@ -0,0 +1,201 @@ +/*
+ * Bezier.java
+ *
+
+ * The Salamander Project - 2D and 3D graphics libraries in Java
+ * Copyright (C) 2004 Mark McKay
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Mark McKay can be contacted at mark@kitfox.com. Salamander and other
+ * projects can be found at http://www.kitfox.com
+ *
+ * Created on January 14, 2005, 4:08 AM
+ */
+
+package com.kitfox.svg.animation;
+
+import java.awt.geom.*;
+
+/**
+ * http://mathworld.wolfram.com/BezierCurve.html
+ * @author kitfox
+ */
+public class Bezier
+{
+ double length;
+ double[] coord;
+
+ public Bezier(double sx, double sy, double[] coords, int numCoords)
+ {
+ setCoords(sx, sy, coords, numCoords);
+ }
+
+ public void setCoords(double sx, double sy, double[] coords, int numCoords)
+ {
+ coord = new double[numCoords * 2 + 2];
+ coord[0] = sx;
+ coord[1] = sy;
+ for (int i = 0; i < numCoords; i++)
+ {
+ coord[i * 2 + 2] = coords[i * 2];
+ coord[i * 2 + 3] = coords[i * 2 + 1];
+ }
+
+ calcLength();
+ }
+
+ /**
+ * Retuns aproximation of the length of the bezier
+ */
+ public double getLength()
+ {
+ return length;
+ }
+
+ private void calcLength()
+ {
+ length = 0;
+ for (int i = 2; i < coord.length; i += 2)
+ {
+ length += lineLength(coord[i - 2], coord[i - 1], coord[i], coord[i + 1]);
+ }
+ }
+
+ private double lineLength(double x1, double y1, double x2, double y2)
+ {
+ double dx = x2 - x1, dy = y2 - y1;
+ return Math.sqrt(dx * dx + dy * dy);
+ }
+
+ public Point2D.Double getFinalPoint(Point2D.Double point)
+ {
+ point.x = coord[coord.length - 2];
+ point.y = coord[coord.length - 1];
+ return point;
+ }
+
+ public Point2D.Double eval(double param, Point2D.Double point)
+ {
+ point.x = 0;
+ point.y = 0;
+ int numKnots = coord.length / 2;
+
+ for (int i = 0; i < numKnots; i++)
+ {
+ double scale = bernstein(numKnots - 1, i, param);
+ point.x += coord[i * 2] * scale;
+ point.y += coord[i * 2 + 1] * scale;
+ }
+
+ return point;
+ }
+
+ /**
+ * Calculates the bernstein polynomial for evaluating parametric bezier
+ * @param numKnots - one less than number of knots in this curve hull
+ * @param knotNo - knot we are evaluating Bernstein for
+ * @param param - Parametric value we are evaluating at
+ */
+ private double bernstein(int numKnots, int knotNo, double param)
+ {
+ double iParam = 1 - param;
+ //Faster evaluation for easy cases:
+ switch (numKnots)
+ {
+ case 0:
+ return 1;
+ case 1:
+ {
+ switch (knotNo)
+ {
+ case 0:
+ return iParam;
+ case 1:
+ return param;
+ }
+ break;
+ }
+ case 2:
+ {
+ switch (knotNo)
+ {
+ case 0:
+ return iParam * iParam;
+ case 1:
+ return 2 * iParam * param;
+ case 2:
+ return param * param;
+ }
+ break;
+ }
+ case 3:
+ {
+ switch (knotNo)
+ {
+ case 0:
+ return iParam * iParam * iParam;
+ case 1:
+ return 3 * iParam * iParam * param;
+ case 2:
+ return 3 * iParam * param * param;
+ case 3:
+ return param * param * param;
+ }
+ break;
+ }
+ }
+
+ //If this bezier has more than four points, calculate bernstein the hard way
+ double retVal = 1;
+ for (int i = 0; i < knotNo; i++)
+ {
+ retVal *= param;
+ }
+ for (int i = 0; i < numKnots - knotNo; i++)
+ {
+ retVal *= iParam;
+ }
+ retVal *= choose(numKnots, knotNo);
+
+ return retVal;
+ }
+
+
+
+ private int choose(int num, int denom)
+ {
+ int denom2 = num - denom;
+ if (denom < denom2)
+ {
+ int tmp = denom;
+ denom = denom2;
+ denom2 = tmp;
+ }
+
+ int prod = 1;
+ for (int i = num; i > denom; i--)
+ {
+ prod *= num;
+ }
+
+ for (int i = 2; i <= denom2; i++)
+ {
+ prod /= i;
+ }
+
+ return prod;
+ }
+}
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