mirror of git://gcc.gnu.org/git/gcc.git
580 lines
15 KiB
Java
580 lines
15 KiB
Java
/* FlatteningPathIterator.java -- Approximates curves by straight lines
|
|
Copyright (C) 2003 Free Software Foundation
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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
|
|
General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
02110-1301 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
|
|
package java.awt.geom;
|
|
|
|
import java.util.NoSuchElementException;
|
|
|
|
|
|
/**
|
|
* A PathIterator for approximating curved path segments by sequences
|
|
* of straight lines. Instances of this class will only return
|
|
* segments of type {@link PathIterator#SEG_MOVETO}, {@link
|
|
* PathIterator#SEG_LINETO}, and {@link PathIterator#SEG_CLOSE}.
|
|
*
|
|
* <p>The accuracy of the approximation is determined by two
|
|
* parameters:
|
|
*
|
|
* <ul><li>The <i>flatness</i> is a threshold value for deciding when
|
|
* a curved segment is consided flat enough for being approximated by
|
|
* a single straight line. Flatness is defined as the maximal distance
|
|
* of a curve control point to the straight line that connects the
|
|
* curve start and end. A lower flatness threshold means a closer
|
|
* approximation. See {@link QuadCurve2D#getFlatness()} and {@link
|
|
* CubicCurve2D#getFlatness()} for drawings which illustrate the
|
|
* meaning of flatness.</li>
|
|
*
|
|
* <li>The <i>recursion limit</i> imposes an upper bound for how often
|
|
* a curved segment gets subdivided. A limit of <i>n</i> means that
|
|
* for each individual quadratic and cubic Bézier spline
|
|
* segment, at most 2<sup><small><i>n</i></small></sup> {@link
|
|
* PathIterator#SEG_LINETO} segments will be created.</li></ul>
|
|
*
|
|
* <p><b>Memory Efficiency:</b> The memory consumption grows linearly
|
|
* with the recursion limit. Neither the <i>flatness</i> parameter nor
|
|
* the number of segments in the flattened path will affect the memory
|
|
* consumption.
|
|
*
|
|
* <p><b>Thread Safety:</b> Multiple threads can safely work on
|
|
* separate instances of this class. However, multiple threads should
|
|
* not concurrently access the same instance, as no synchronization is
|
|
* performed.
|
|
*
|
|
* @see <a href="doc-files/FlatteningPathIterator-1.html"
|
|
* >Implementation Note</a>
|
|
*
|
|
* @author Sascha Brawer (brawer@dandelis.ch)
|
|
*
|
|
* @since 1.2
|
|
*/
|
|
public class FlatteningPathIterator
|
|
implements PathIterator
|
|
{
|
|
/**
|
|
* The PathIterator whose curved segments are being approximated.
|
|
*/
|
|
private final PathIterator srcIter;
|
|
|
|
|
|
/**
|
|
* The square of the flatness threshold value, which determines when
|
|
* a curve segment is considered flat enough that no further
|
|
* subdivision is needed.
|
|
*
|
|
* <p>Calculating flatness actually produces the squared flatness
|
|
* value. To avoid the relatively expensive calculation of a square
|
|
* root for each curve segment, we perform all flatness comparisons
|
|
* on squared values.
|
|
*
|
|
* @see QuadCurve2D#getFlatnessSq()
|
|
* @see CubicCurve2D#getFlatnessSq()
|
|
*/
|
|
private final double flatnessSq;
|
|
|
|
|
|
/**
|
|
* The maximal number of subdivions that are performed to
|
|
* approximate a quadratic or cubic curve segment.
|
|
*/
|
|
private final int recursionLimit;
|
|
|
|
|
|
/**
|
|
* A stack for holding the coordinates of subdivided segments.
|
|
*
|
|
* @see <a href="doc-files/FlatteningPathIterator-1.html"
|
|
* >Implementation Note</a>
|
|
*/
|
|
private double[] stack;
|
|
|
|
|
|
/**
|
|
* The current stack size.
|
|
*
|
|
* @see <a href="doc-files/FlatteningPathIterator-1.html"
|
|
* >Implementation Note</a>
|
|
*/
|
|
private int stackSize;
|
|
|
|
|
|
/**
|
|
* The number of recursions that were performed to arrive at
|
|
* a segment on the stack.
|
|
*
|
|
* @see <a href="doc-files/FlatteningPathIterator-1.html"
|
|
* >Implementation Note</a>
|
|
*/
|
|
private int[] recLevel;
|
|
|
|
|
|
|
|
private final double[] scratch = new double[6];
|
|
|
|
|
|
/**
|
|
* The segment type of the last segment that was returned by
|
|
* the source iterator.
|
|
*/
|
|
private int srcSegType;
|
|
|
|
|
|
/**
|
|
* The current <i>x</i> position of the source iterator.
|
|
*/
|
|
private double srcPosX;
|
|
|
|
|
|
/**
|
|
* The current <i>y</i> position of the source iterator.
|
|
*/
|
|
private double srcPosY;
|
|
|
|
|
|
/**
|
|
* A flag that indicates when this path iterator has finished its
|
|
* iteration over path segments.
|
|
*/
|
|
private boolean done;
|
|
|
|
|
|
/**
|
|
* Constructs a new PathIterator for approximating an input
|
|
* PathIterator with straight lines. The approximation works by
|
|
* recursive subdivisons, until the specified flatness threshold is
|
|
* not exceeded.
|
|
*
|
|
* <p>There will not be more than 10 nested recursion steps, which
|
|
* means that a single <code>SEG_QUADTO</code> or
|
|
* <code>SEG_CUBICTO</code> segment is approximated by at most
|
|
* 2<sup><small>10</small></sup> = 1024 straight lines.
|
|
*/
|
|
public FlatteningPathIterator(PathIterator src, double flatness)
|
|
{
|
|
this(src, flatness, 10);
|
|
}
|
|
|
|
|
|
/**
|
|
* Constructs a new PathIterator for approximating an input
|
|
* PathIterator with straight lines. The approximation works by
|
|
* recursive subdivisons, until the specified flatness threshold is
|
|
* not exceeded. Additionally, the number of recursions is also
|
|
* bound by the specified recursion limit.
|
|
*/
|
|
public FlatteningPathIterator(PathIterator src, double flatness,
|
|
int limit)
|
|
{
|
|
if (flatness < 0 || limit < 0)
|
|
throw new IllegalArgumentException();
|
|
|
|
srcIter = src;
|
|
flatnessSq = flatness * flatness;
|
|
recursionLimit = limit;
|
|
fetchSegment();
|
|
}
|
|
|
|
|
|
/**
|
|
* Returns the maximally acceptable flatness.
|
|
*
|
|
* @see QuadCurve2D#getFlatness()
|
|
* @see CubicCurve2D#getFlatness()
|
|
*/
|
|
public double getFlatness()
|
|
{
|
|
return Math.sqrt(flatnessSq);
|
|
}
|
|
|
|
|
|
/**
|
|
* Returns the maximum number of recursive curve subdivisions.
|
|
*/
|
|
public int getRecursionLimit()
|
|
{
|
|
return recursionLimit;
|
|
}
|
|
|
|
|
|
// Documentation will be copied from PathIterator.
|
|
public int getWindingRule()
|
|
{
|
|
return srcIter.getWindingRule();
|
|
}
|
|
|
|
|
|
// Documentation will be copied from PathIterator.
|
|
public boolean isDone()
|
|
{
|
|
return done;
|
|
}
|
|
|
|
|
|
// Documentation will be copied from PathIterator.
|
|
public void next()
|
|
{
|
|
if (stackSize > 0)
|
|
{
|
|
--stackSize;
|
|
if (stackSize > 0)
|
|
{
|
|
switch (srcSegType)
|
|
{
|
|
case PathIterator.SEG_QUADTO:
|
|
subdivideQuadratic();
|
|
return;
|
|
|
|
case PathIterator.SEG_CUBICTO:
|
|
subdivideCubic();
|
|
return;
|
|
|
|
default:
|
|
throw new IllegalStateException();
|
|
}
|
|
}
|
|
}
|
|
|
|
srcIter.next();
|
|
fetchSegment();
|
|
}
|
|
|
|
|
|
// Documentation will be copied from PathIterator.
|
|
public int currentSegment(double[] coords)
|
|
{
|
|
if (done)
|
|
throw new NoSuchElementException();
|
|
|
|
switch (srcSegType)
|
|
{
|
|
case PathIterator.SEG_CLOSE:
|
|
return srcSegType;
|
|
|
|
case PathIterator.SEG_MOVETO:
|
|
case PathIterator.SEG_LINETO:
|
|
coords[0] = srcPosX;
|
|
coords[1] = srcPosY;
|
|
return srcSegType;
|
|
|
|
case PathIterator.SEG_QUADTO:
|
|
if (stackSize == 0)
|
|
{
|
|
coords[0] = srcPosX;
|
|
coords[1] = srcPosY;
|
|
}
|
|
else
|
|
{
|
|
int sp = stack.length - 4 * stackSize;
|
|
coords[0] = stack[sp + 2];
|
|
coords[1] = stack[sp + 3];
|
|
}
|
|
return PathIterator.SEG_LINETO;
|
|
|
|
case PathIterator.SEG_CUBICTO:
|
|
if (stackSize == 0)
|
|
{
|
|
coords[0] = srcPosX;
|
|
coords[1] = srcPosY;
|
|
}
|
|
else
|
|
{
|
|
int sp = stack.length - 6 * stackSize;
|
|
coords[0] = stack[sp + 4];
|
|
coords[1] = stack[sp + 5];
|
|
}
|
|
return PathIterator.SEG_LINETO;
|
|
}
|
|
|
|
throw new IllegalStateException();
|
|
}
|
|
|
|
|
|
// Documentation will be copied from PathIterator.
|
|
public int currentSegment(float[] coords)
|
|
{
|
|
if (done)
|
|
throw new NoSuchElementException();
|
|
|
|
switch (srcSegType)
|
|
{
|
|
case PathIterator.SEG_CLOSE:
|
|
return srcSegType;
|
|
|
|
case PathIterator.SEG_MOVETO:
|
|
case PathIterator.SEG_LINETO:
|
|
coords[0] = (float) srcPosX;
|
|
coords[1] = (float) srcPosY;
|
|
return srcSegType;
|
|
|
|
case PathIterator.SEG_QUADTO:
|
|
if (stackSize == 0)
|
|
{
|
|
coords[0] = (float) srcPosX;
|
|
coords[1] = (float) srcPosY;
|
|
}
|
|
else
|
|
{
|
|
int sp = stack.length - 4 * stackSize;
|
|
coords[0] = (float) stack[sp + 2];
|
|
coords[1] = (float) stack[sp + 3];
|
|
}
|
|
return PathIterator.SEG_LINETO;
|
|
|
|
case PathIterator.SEG_CUBICTO:
|
|
if (stackSize == 0)
|
|
{
|
|
coords[0] = (float) srcPosX;
|
|
coords[1] = (float) srcPosY;
|
|
}
|
|
else
|
|
{
|
|
int sp = stack.length - 6 * stackSize;
|
|
coords[0] = (float) stack[sp + 4];
|
|
coords[1] = (float) stack[sp + 5];
|
|
}
|
|
return PathIterator.SEG_LINETO;
|
|
}
|
|
|
|
throw new IllegalStateException();
|
|
}
|
|
|
|
|
|
/**
|
|
* Fetches the next segment from the source iterator.
|
|
*/
|
|
private void fetchSegment()
|
|
{
|
|
int sp;
|
|
|
|
if (srcIter.isDone())
|
|
{
|
|
done = true;
|
|
return;
|
|
}
|
|
|
|
srcSegType = srcIter.currentSegment(scratch);
|
|
|
|
switch (srcSegType)
|
|
{
|
|
case PathIterator.SEG_CLOSE:
|
|
return;
|
|
|
|
case PathIterator.SEG_MOVETO:
|
|
case PathIterator.SEG_LINETO:
|
|
srcPosX = scratch[0];
|
|
srcPosY = scratch[1];
|
|
return;
|
|
|
|
case PathIterator.SEG_QUADTO:
|
|
if (recursionLimit == 0)
|
|
{
|
|
srcPosX = scratch[2];
|
|
srcPosY = scratch[3];
|
|
stackSize = 0;
|
|
return;
|
|
}
|
|
sp = 4 * recursionLimit;
|
|
stackSize = 1;
|
|
if (stack == null)
|
|
{
|
|
stack = new double[sp + /* 4 + 2 */ 6];
|
|
recLevel = new int[recursionLimit + 1];
|
|
}
|
|
recLevel[0] = 0;
|
|
stack[sp] = srcPosX; // P1.x
|
|
stack[sp + 1] = srcPosY; // P1.y
|
|
stack[sp + 2] = scratch[0]; // C.x
|
|
stack[sp + 3] = scratch[1]; // C.y
|
|
srcPosX = stack[sp + 4] = scratch[2]; // P2.x
|
|
srcPosY = stack[sp + 5] = scratch[3]; // P2.y
|
|
subdivideQuadratic();
|
|
break;
|
|
|
|
case PathIterator.SEG_CUBICTO:
|
|
if (recursionLimit == 0)
|
|
{
|
|
srcPosX = scratch[4];
|
|
srcPosY = scratch[5];
|
|
stackSize = 0;
|
|
return;
|
|
}
|
|
sp = 6 * recursionLimit;
|
|
stackSize = 1;
|
|
if ((stack == null) || (stack.length < sp + 8))
|
|
{
|
|
stack = new double[sp + /* 6 + 2 */ 8];
|
|
recLevel = new int[recursionLimit + 1];
|
|
}
|
|
recLevel[0] = 0;
|
|
stack[sp] = srcPosX; // P1.x
|
|
stack[sp + 1] = srcPosY; // P1.y
|
|
stack[sp + 2] = scratch[0]; // C1.x
|
|
stack[sp + 3] = scratch[1]; // C1.y
|
|
stack[sp + 4] = scratch[2]; // C2.x
|
|
stack[sp + 5] = scratch[3]; // C2.y
|
|
srcPosX = stack[sp + 6] = scratch[4]; // P2.x
|
|
srcPosY = stack[sp + 7] = scratch[5]; // P2.y
|
|
subdivideCubic();
|
|
return;
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Repeatedly subdivides the quadratic curve segment that is on top
|
|
* of the stack. The iteration terminates when the recursion limit
|
|
* has been reached, or when the resulting segment is flat enough.
|
|
*/
|
|
private void subdivideQuadratic()
|
|
{
|
|
int sp;
|
|
int level;
|
|
|
|
sp = stack.length - 4 * stackSize - 2;
|
|
level = recLevel[stackSize - 1];
|
|
while ((level < recursionLimit)
|
|
&& (QuadCurve2D.getFlatnessSq(stack, sp) >= flatnessSq))
|
|
{
|
|
recLevel[stackSize] = recLevel[stackSize - 1] = ++level;
|
|
QuadCurve2D.subdivide(stack, sp, stack, sp - 4, stack, sp);
|
|
++stackSize;
|
|
sp -= 4;
|
|
}
|
|
}
|
|
|
|
|
|
/**
|
|
* Repeatedly subdivides the cubic curve segment that is on top
|
|
* of the stack. The iteration terminates when the recursion limit
|
|
* has been reached, or when the resulting segment is flat enough.
|
|
*/
|
|
private void subdivideCubic()
|
|
{
|
|
int sp;
|
|
int level;
|
|
|
|
sp = stack.length - 6 * stackSize - 2;
|
|
level = recLevel[stackSize - 1];
|
|
while ((level < recursionLimit)
|
|
&& (CubicCurve2D.getFlatnessSq(stack, sp) >= flatnessSq))
|
|
{
|
|
recLevel[stackSize] = recLevel[stackSize - 1] = ++level;
|
|
|
|
CubicCurve2D.subdivide(stack, sp, stack, sp - 6, stack, sp);
|
|
++stackSize;
|
|
sp -= 6;
|
|
}
|
|
}
|
|
|
|
|
|
/* These routines were useful for debugging. Since they would
|
|
* just bloat the implementation, they are commented out.
|
|
*
|
|
*
|
|
|
|
private static String segToString(int segType, double[] d, int offset)
|
|
{
|
|
String s;
|
|
|
|
switch (segType)
|
|
{
|
|
case PathIterator.SEG_CLOSE:
|
|
return "SEG_CLOSE";
|
|
|
|
case PathIterator.SEG_MOVETO:
|
|
return "SEG_MOVETO (" + d[offset] + ", " + d[offset + 1] + ")";
|
|
|
|
case PathIterator.SEG_LINETO:
|
|
return "SEG_LINETO (" + d[offset] + ", " + d[offset + 1] + ")";
|
|
|
|
case PathIterator.SEG_QUADTO:
|
|
return "SEG_QUADTO (" + d[offset] + ", " + d[offset + 1]
|
|
+ ") (" + d[offset + 2] + ", " + d[offset + 3] + ")";
|
|
|
|
case PathIterator.SEG_CUBICTO:
|
|
return "SEG_CUBICTO (" + d[offset] + ", " + d[offset + 1]
|
|
+ ") (" + d[offset + 2] + ", " + d[offset + 3]
|
|
+ ") (" + d[offset + 4] + ", " + d[offset + 5] + ")";
|
|
}
|
|
|
|
throw new IllegalStateException();
|
|
}
|
|
|
|
|
|
private void dumpQuadraticStack(String msg)
|
|
{
|
|
int sp = stack.length - 4 * stackSize - 2;
|
|
int i = 0;
|
|
System.err.print(" " + msg + ":");
|
|
while (sp < stack.length)
|
|
{
|
|
System.err.print(" (" + stack[sp] + ", " + stack[sp+1] + ")");
|
|
if (i < recLevel.length)
|
|
System.out.print("/" + recLevel[i++]);
|
|
if (sp + 3 < stack.length)
|
|
System.err.print(" [" + stack[sp+2] + ", " + stack[sp+3] + "]");
|
|
sp += 4;
|
|
}
|
|
System.err.println();
|
|
}
|
|
|
|
|
|
private void dumpCubicStack(String msg)
|
|
{
|
|
int sp = stack.length - 6 * stackSize - 2;
|
|
int i = 0;
|
|
System.err.print(" " + msg + ":");
|
|
while (sp < stack.length)
|
|
{
|
|
System.err.print(" (" + stack[sp] + ", " + stack[sp+1] + ")");
|
|
if (i < recLevel.length)
|
|
System.out.print("/" + recLevel[i++]);
|
|
if (sp + 3 < stack.length)
|
|
{
|
|
System.err.print(" [" + stack[sp+2] + ", " + stack[sp+3] + "]");
|
|
System.err.print(" [" + stack[sp+4] + ", " + stack[sp+5] + "]");
|
|
}
|
|
sp += 6;
|
|
}
|
|
System.err.println();
|
|
}
|
|
|
|
*
|
|
*
|
|
*/
|
|
}
|