/*
* SVG Salamander
* Copyright (c) 2004, Mark McKay
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the following
* disclaimer.
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials
* provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Mark McKay can be contacted at mark@kitfox.com. Salamander and other
* projects can be found at http://www.kitfox.com
*
* Created on January 26, 2004, 8:40 PM
*/
package com.kitfox.svg.pathcmd;
//import org.apache.batik.ext.awt.geom.ExtendedGeneralPath;
import java.awt.*;
import java.awt.geom.*;
/**
* This is a little used SVG function, as most editors will save curves as
* Beziers. To reduce the need to rely on the Batik library, this functionallity
* is being bypassed for the time being. In the future, it would be nice to
* extend the GeneralPath command to include the arcTo ability provided by Batik.
*
* @author Mark McKay
* @author <a href="mailto:mark@kitfox.com">Mark McKay</a>
*/
public class Arc extends PathCommand
{
public float rx = 0f;
public float ry = 0f;
public float xAxisRot = 0f;
public boolean largeArc = false;
public boolean sweep = false;
public float x = 0f;
public float y = 0f;
/** Creates a new instance of MoveTo */
public Arc() {
}
public Arc(boolean isRelative, float rx, float ry, float xAxisRot, boolean largeArc, boolean sweep, float x, float y) {
super(isRelative);
this.rx = rx;
this.ry = ry;
this.xAxisRot = xAxisRot;
this.largeArc = largeArc;
this.sweep = sweep;
this.x = x;
this.y = y;
}
// public void appendPath(ExtendedGeneralPath path, BuildHistory hist)
public void appendPath(GeneralPath path, BuildHistory hist)
{
float offx = isRelative ? hist.lastPoint.x : 0f;
float offy = isRelative ? hist.lastPoint.y : 0f;
arcTo(path, rx, ry, xAxisRot, largeArc, sweep,
x + offx, y + offy,
hist.lastPoint.x, hist.lastPoint.y);
// path.lineTo(x + offx, y + offy);
// hist.setPoint(x + offx, y + offy);
hist.setLastPoint(x + offx, y + offy);
hist.setLastKnot(x + offx, y + offy);
}
public int getNumKnotsAdded()
{
return 6;
}
/**
* Adds an elliptical arc, defined by two radii, an angle from the
* x-axis, a flag to choose the large arc or not, a flag to
* indicate if we increase or decrease the angles and the final
* point of the arc.
*
* @param rx the x radius of the ellipse
* @param ry the y radius of the ellipse
*
* @param angle the angle from the x-axis of the current
* coordinate system to the x-axis of the ellipse in degrees.
*
* @param largeArcFlag the large arc flag. If true the arc
* spanning less than or equal to 180 degrees is chosen, otherwise
* the arc spanning greater than 180 degrees is chosen
*
* @param sweepFlag the sweep flag. If true the line joining
* center to arc sweeps through decreasing angles otherwise it
* sweeps through increasing angles
*
* @param x the absolute x coordinate of the final point of the arc.
* @param y the absolute y coordinate of the final point of the arc.
* @param x0 - The absolute x coordinate of the initial point of the arc.
* @param y0 - The absolute y coordinate of the initial point of the arc.
*/
public void arcTo(GeneralPath path, float rx, float ry,
float angle,
boolean largeArcFlag,
boolean sweepFlag,
float x, float y, float x0, float y0)
{
// Ensure radii are valid
if (rx == 0 || ry == 0) {
path.lineTo((float) x, (float) y);
return;
}
if (x0 == x && y0 == y) {
// If the endpoints (x, y) and (x0, y0) are identical, then this
// is equivalent to omitting the elliptical arc segment entirely.
return;
}
Arc2D arc = computeArc(x0, y0, rx, ry, angle,
largeArcFlag, sweepFlag, x, y);
if (arc == null) return;
AffineTransform t = AffineTransform.getRotateInstance
(Math.toRadians(angle), arc.getCenterX(), arc.getCenterY());
Shape s = t.createTransformedShape(arc);
path.append(s, true);
}
/**
* This constructs an unrotated Arc2D from the SVG specification of an
* Elliptical arc. To get the final arc you need to apply a rotation
* transform such as:
*
* AffineTransform.getRotateInstance
* (angle, arc.getX()+arc.getWidth()/2, arc.getY()+arc.getHeight()/2);
*/
public static Arc2D computeArc(double x0, double y0,
double rx, double ry,
double angle,
boolean largeArcFlag,
boolean sweepFlag,
double x, double y) {
//
// Elliptical arc implementation based on the SVG specification notes
//
// Compute the half distance between the current and the final point
double dx2 = (x0 - x) / 2.0;
double dy2 = (y0 - y) / 2.0;
// Convert angle from degrees to radians
angle = Math.toRadians(angle % 360.0);
double cosAngle = Math.cos(angle);
double sinAngle = Math.sin(angle);
//
// Step 1 : Compute (x1, y1)
//
double x1 = (cosAngle * dx2 + sinAngle * dy2);
double y1 = (-sinAngle * dx2 + cosAngle * dy2);
// Ensure radii are large enough
rx = Math.abs(rx);
ry = Math.abs(ry);
double Prx = rx * rx;
double Pry = ry * ry;
double Px1 = x1 * x1;
double Py1 = y1 * y1;
// check that radii are large enough
double radiiCheck = Px1/Prx + Py1/Pry;
if (radiiCheck > 1) {
rx = Math.sqrt(radiiCheck) * rx;
ry = Math.sqrt(radiiCheck) * ry;
Prx = rx * rx;
Pry = ry * ry;
}
//
// Step 2 : Compute (cx1, cy1)
//
double sign = (largeArcFlag == sweepFlag) ? -1 : 1;
double sq = ((Prx*Pry)-(Prx*Py1)-(Pry*Px1)) / ((Prx*Py1)+(Pry*Px1));
sq = (sq < 0) ? 0 : sq;
double coef = (sign * Math.sqrt(sq));
double cx1 = coef * ((rx * y1) / ry);
double cy1 = coef * -((ry * x1) / rx);
//
// Step 3 : Compute (cx, cy) from (cx1, cy1)
//
double sx2 = (x0 + x) / 2.0;
double sy2 = (y0 + y) / 2.0;
double cx = sx2 + (cosAngle * cx1 - sinAngle * cy1);
double cy = sy2 + (sinAngle * cx1 + cosAngle * cy1);
//
// Step 4 : Compute the angleStart (angle1) and the angleExtent (dangle)
//
double ux = (x1 - cx1) / rx;
double uy = (y1 - cy1) / ry;
double vx = (-x1 - cx1) / rx;
double vy = (-y1 - cy1) / ry;
double p, n;
// Compute the angle start
n = Math.sqrt((ux * ux) + (uy * uy));
p = ux; // (1 * ux) + (0 * uy)
sign = (uy < 0) ? -1d : 1d;
double angleStart = Math.toDegrees(sign * Math.acos(p / n));
// Compute the angle extent
n = Math.sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy));
p = ux * vx + uy * vy;
sign = (ux * vy - uy * vx < 0) ? -1d : 1d;
double angleExtent = Math.toDegrees(sign * Math.acos(p / n));
if(!sweepFlag && angleExtent > 0) {
angleExtent -= 360f;
} else if (sweepFlag && angleExtent < 0) {
angleExtent += 360f;
}
angleExtent %= 360f;
angleStart %= 360f;
//
// We can now build the resulting Arc2D in double precision
//
Arc2D.Double arc = new Arc2D.Double();
arc.x = cx - rx;
arc.y = cy - ry;
arc.width = rx * 2.0;
arc.height = ry * 2.0;
arc.start = -angleStart;
arc.extent = -angleExtent;
return arc;
}
public String toString()
{
return "A " + rx + " " + ry
+ " " + xAxisRot + " " + largeArc
+ " " + sweep
+ " " + x + " " + y;
}
}
