java.awt.geom

Class FlatteningPathIterator

Implemented Interfaces:
PathIterator

public class FlatteningPathIterator
extends Object
implements PathIterator

A PathIterator for approximating curved path segments by sequences of straight lines. Instances of this class will only return segments of type PathIterator.SEG_MOVETO, PathIterator.SEG_LINETO, and PathIterator.SEG_CLOSE.

The accuracy of the approximation is determined by two parameters:

Memory Efficiency: The memory consumption grows linearly with the recursion limit. Neither the flatness parameter nor the number of segments in the flattened path will affect the memory consumption.

Thread Safety: 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.

Since:
1.2
See Also:
Implementation Note

Fields inherited from interface java.awt.geom.PathIterator

SEG_CLOSE, SEG_CUBICTO, SEG_LINETO, SEG_MOVETO, SEG_QUADTO, WIND_EVEN_ODD, WIND_NON_ZERO

Constructor Summary

FlatteningPathIterator(PathIterator src, double flatness)
Constructs a new PathIterator for approximating an input PathIterator with straight lines.
FlatteningPathIterator(PathIterator src, double flatness, int limit)
Constructs a new PathIterator for approximating an input PathIterator with straight lines.

Method Summary

int
currentSegment(double[] coords)
Returns the coordinates of the next point(s), as well as the type of line segment.
int
currentSegment(float[] coords)
Returns the coordinates of the next point(s), as well as the type of line segment.
double
getFlatness()
Returns the maximally acceptable flatness.
int
getRecursionLimit()
Returns the maximum number of recursive curve subdivisions.
int
getWindingRule()
Returns the winding rule to determine which points are inside this path.
boolean
isDone()
Tests if the iterator is exhausted.
void
next()
Advance to the next segment in the iteration.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

FlatteningPathIterator

public FlatteningPathIterator(PathIterator src,
                              double flatness)
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.

There will not be more than 10 nested recursion steps, which means that a single SEG_QUADTO or SEG_CUBICTO segment is approximated by at most 210 = 1024 straight lines.


FlatteningPathIterator

public FlatteningPathIterator(PathIterator src,
                              double flatness,
                              int limit)
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.

Method Details

currentSegment

public int currentSegment(double[] coords)
Returns the coordinates of the next point(s), as well as the type of line segment. The input array must be at least a double[6], to accomodate up to three (x,y) point pairs (although if you know the iterator is flat, you can probably get by with a double[2]). If the returned type is SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if the returned type is SEG_QUADTO, the first two points are modified; if the returned type is SEG_CUBICTO, all three points are modified; and if the returned type is SEG_CLOSE, the array is untouched.
Specified by:
currentSegment in interface PathIterator
Parameters:
coords - the array to place the point coordinates in
Returns:
the segment type
Throws:
NullPointerException - if coords is null
ArrayIndexOutOfBoundsException - if coords is too small
NoSuchElementException - optional when isDone() is true

currentSegment

public int currentSegment(float[] coords)
Returns the coordinates of the next point(s), as well as the type of line segment. The input array must be at least a float[6], to accomodate up to three (x,y) point pairs (although if you know the iterator is flat, you can probably get by with a float[2]). If the returned type is SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if the returned type is SEG_QUADTO, the first two points are modified; if the returned type is SEG_CUBICTO, all three points are modified; and if the returned type is SEG_CLOSE, the array is untouched.
Specified by:
currentSegment in interface PathIterator
Parameters:
coords - the array to place the point coordinates in
Returns:
the segment type
Throws:
NullPointerException - if coords is null
ArrayIndexOutOfBoundsException - if coords is too small
NoSuchElementException - optional when isDone() is true

getFlatness

public double getFlatness()
Returns the maximally acceptable flatness.

getRecursionLimit

public int getRecursionLimit()
Returns the maximum number of recursive curve subdivisions.

getWindingRule

public int getWindingRule()
Returns the winding rule to determine which points are inside this path.
Specified by:
getWindingRule in interface PathIterator
Returns:
the winding rule

isDone

public boolean isDone()
Tests if the iterator is exhausted. If this returns true, currentSegment and next may throw a NoSuchElementException (although this is not required).
Specified by:
isDone in interface PathIterator
Returns:
true if the iteration is complete

next

public void next()
Advance to the next segment in the iteration. It is not specified what this does if called when isDone() returns true.
Specified by:
next in interface PathIterator
Throws:
NoSuchElementException - optional when isDone() is true

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.