Java example source code file (Crossings.java)
The Crossings.java Java example source code
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package sun.awt.geom;
import java.awt.geom.PathIterator;
import java.util.Vector;
import java.util.Enumeration;
public abstract class Crossings {
public static final boolean debug = false;
int limit = 0;
double yranges[] = new double[10];
double xlo, ylo, xhi, yhi;
public Crossings(double xlo, double ylo, double xhi, double yhi) {
this.xlo = xlo;
this.ylo = ylo;
this.xhi = xhi;
this.yhi = yhi;
}
public final double getXLo() {
return xlo;
}
public final double getYLo() {
return ylo;
}
public final double getXHi() {
return xhi;
}
public final double getYHi() {
return yhi;
}
public abstract void record(double ystart, double yend, int direction);
public void print() {
System.out.println("Crossings [");
System.out.println(" bounds = ["+ylo+", "+yhi+"]");
for (int i = 0; i < limit; i += 2) {
System.out.println(" ["+yranges[i]+", "+yranges[i+1]+"]");
}
System.out.println("]");
}
public final boolean isEmpty() {
return (limit == 0);
}
public abstract boolean covers(double ystart, double yend);
public static Crossings findCrossings(Vector curves,
double xlo, double ylo,
double xhi, double yhi)
{
Crossings cross = new EvenOdd(xlo, ylo, xhi, yhi);
Enumeration enum_ = curves.elements();
while (enum_.hasMoreElements()) {
Curve c = (Curve) enum_.nextElement();
if (c.accumulateCrossings(cross)) {
return null;
}
}
if (debug) {
cross.print();
}
return cross;
}
public static Crossings findCrossings(PathIterator pi,
double xlo, double ylo,
double xhi, double yhi)
{
Crossings cross;
if (pi.getWindingRule() == pi.WIND_EVEN_ODD) {
cross = new EvenOdd(xlo, ylo, xhi, yhi);
} else {
cross = new NonZero(xlo, ylo, xhi, yhi);
}
// coords array is big enough for holding:
// coordinates returned from currentSegment (6)
// OR
// two subdivided quadratic curves (2+4+4=10)
// AND
// 0-1 horizontal splitting parameters
// OR
// 2 parametric equation derivative coefficients
// OR
// three subdivided cubic curves (2+6+6+6=20)
// AND
// 0-2 horizontal splitting parameters
// OR
// 3 parametric equation derivative coefficients
double coords[] = new double[23];
double movx = 0;
double movy = 0;
double curx = 0;
double cury = 0;
double newx, newy;
while (!pi.isDone()) {
int type = pi.currentSegment(coords);
switch (type) {
case PathIterator.SEG_MOVETO:
if (movy != cury &&
cross.accumulateLine(curx, cury, movx, movy))
{
return null;
}
movx = curx = coords[0];
movy = cury = coords[1];
break;
case PathIterator.SEG_LINETO:
newx = coords[0];
newy = coords[1];
if (cross.accumulateLine(curx, cury, newx, newy)) {
return null;
}
curx = newx;
cury = newy;
break;
case PathIterator.SEG_QUADTO:
newx = coords[2];
newy = coords[3];
if (cross.accumulateQuad(curx, cury, coords)) {
return null;
}
curx = newx;
cury = newy;
break;
case PathIterator.SEG_CUBICTO:
newx = coords[4];
newy = coords[5];
if (cross.accumulateCubic(curx, cury, coords)) {
return null;
}
curx = newx;
cury = newy;
break;
case PathIterator.SEG_CLOSE:
if (movy != cury &&
cross.accumulateLine(curx, cury, movx, movy))
{
return null;
}
curx = movx;
cury = movy;
break;
}
pi.next();
}
if (movy != cury) {
if (cross.accumulateLine(curx, cury, movx, movy)) {
return null;
}
}
if (debug) {
cross.print();
}
return cross;
}
public boolean accumulateLine(double x0, double y0,
double x1, double y1)
{
if (y0 <= y1) {
return accumulateLine(x0, y0, x1, y1, 1);
} else {
return accumulateLine(x1, y1, x0, y0, -1);
}
}
public boolean accumulateLine(double x0, double y0,
double x1, double y1,
int direction)
{
if (yhi <= y0 || ylo >= y1) {
return false;
}
if (x0 >= xhi && x1 >= xhi) {
return false;
}
if (y0 == y1) {
return (x0 >= xlo || x1 >= xlo);
}
double xstart, ystart, xend, yend;
double dx = (x1 - x0);
double dy = (y1 - y0);
if (y0 < ylo) {
xstart = x0 + (ylo - y0) * dx / dy;
ystart = ylo;
} else {
xstart = x0;
ystart = y0;
}
if (yhi < y1) {
xend = x0 + (yhi - y0) * dx / dy;
yend = yhi;
} else {
xend = x1;
yend = y1;
}
if (xstart >= xhi && xend >= xhi) {
return false;
}
if (xstart > xlo || xend > xlo) {
return true;
}
record(ystart, yend, direction);
return false;
}
private Vector tmp = new Vector();
public boolean accumulateQuad(double x0, double y0, double coords[]) {
if (y0 < ylo && coords[1] < ylo && coords[3] < ylo) {
return false;
}
if (y0 > yhi && coords[1] > yhi && coords[3] > yhi) {
return false;
}
if (x0 > xhi && coords[0] > xhi && coords[2] > xhi) {
return false;
}
if (x0 < xlo && coords[0] < xlo && coords[2] < xlo) {
if (y0 < coords[3]) {
record(Math.max(y0, ylo), Math.min(coords[3], yhi), 1);
} else if (y0 > coords[3]) {
record(Math.max(coords[3], ylo), Math.min(y0, yhi), -1);
}
return false;
}
Curve.insertQuad(tmp, x0, y0, coords);
Enumeration enum_ = tmp.elements();
while (enum_.hasMoreElements()) {
Curve c = (Curve) enum_.nextElement();
if (c.accumulateCrossings(this)) {
return true;
}
}
tmp.clear();
return false;
}
public boolean accumulateCubic(double x0, double y0, double coords[]) {
if (y0 < ylo && coords[1] < ylo &&
coords[3] < ylo && coords[5] < ylo)
{
return false;
}
if (y0 > yhi && coords[1] > yhi &&
coords[3] > yhi && coords[5] > yhi)
{
return false;
}
if (x0 > xhi && coords[0] > xhi &&
coords[2] > xhi && coords[4] > xhi)
{
return false;
}
if (x0 < xlo && coords[0] < xlo &&
coords[2] < xlo && coords[4] < xlo)
{
if (y0 <= coords[5]) {
record(Math.max(y0, ylo), Math.min(coords[5], yhi), 1);
} else {
record(Math.max(coords[5], ylo), Math.min(y0, yhi), -1);
}
return false;
}
Curve.insertCubic(tmp, x0, y0, coords);
Enumeration enum_ = tmp.elements();
while (enum_.hasMoreElements()) {
Curve c = (Curve) enum_.nextElement();
if (c.accumulateCrossings(this)) {
return true;
}
}
tmp.clear();
return false;
}
public final static class EvenOdd extends Crossings {
public EvenOdd(double xlo, double ylo, double xhi, double yhi) {
super(xlo, ylo, xhi, yhi);
}
public final boolean covers(double ystart, double yend) {
return (limit == 2 && yranges[0] <= ystart && yranges[1] >= yend);
}
public void record(double ystart, double yend, int direction) {
if (ystart >= yend) {
return;
}
int from = 0;
// Quickly jump over all pairs that are completely "above"
while (from < limit && ystart > yranges[from+1]) {
from += 2;
}
int to = from;
while (from < limit) {
double yrlo = yranges[from++];
double yrhi = yranges[from++];
if (yend < yrlo) {
// Quickly handle insertion of the new range
yranges[to++] = ystart;
yranges[to++] = yend;
ystart = yrlo;
yend = yrhi;
continue;
}
// The ranges overlap - sort, collapse, insert, iterate
double yll, ylh, yhl, yhh;
if (ystart < yrlo) {
yll = ystart;
ylh = yrlo;
} else {
yll = yrlo;
ylh = ystart;
}
if (yend < yrhi) {
yhl = yend;
yhh = yrhi;
} else {
yhl = yrhi;
yhh = yend;
}
if (ylh == yhl) {
ystart = yll;
yend = yhh;
} else {
if (ylh > yhl) {
ystart = yhl;
yhl = ylh;
ylh = ystart;
}
if (yll != ylh) {
yranges[to++] = yll;
yranges[to++] = ylh;
}
ystart = yhl;
yend = yhh;
}
if (ystart >= yend) {
break;
}
}
if (to < from && from < limit) {
System.arraycopy(yranges, from, yranges, to, limit-from);
}
to += (limit-from);
if (ystart < yend) {
if (to >= yranges.length) {
double newranges[] = new double[to+10];
System.arraycopy(yranges, 0, newranges, 0, to);
yranges = newranges;
}
yranges[to++] = ystart;
yranges[to++] = yend;
}
limit = to;
}
}
public final static class NonZero extends Crossings {
private int crosscounts[];
public NonZero(double xlo, double ylo, double xhi, double yhi) {
super(xlo, ylo, xhi, yhi);
crosscounts = new int[yranges.length / 2];
}
public final boolean covers(double ystart, double yend) {
int i = 0;
while (i < limit) {
double ylo = yranges[i++];
double yhi = yranges[i++];
if (ystart >= yhi) {
continue;
}
if (ystart < ylo) {
return false;
}
if (yend <= yhi) {
return true;
}
ystart = yhi;
}
return (ystart >= yend);
}
public void remove(int cur) {
limit -= 2;
int rem = limit - cur;
if (rem > 0) {
System.arraycopy(yranges, cur+2, yranges, cur, rem);
System.arraycopy(crosscounts, cur/2+1,
crosscounts, cur/2,
rem/2);
}
}
public void insert(int cur, double lo, double hi, int dir) {
int rem = limit - cur;
double oldranges[] = yranges;
int oldcounts[] = crosscounts;
if (limit >= yranges.length) {
yranges = new double[limit+10];
System.arraycopy(oldranges, 0, yranges, 0, cur);
crosscounts = new int[(limit+10)/2];
System.arraycopy(oldcounts, 0, crosscounts, 0, cur/2);
}
if (rem > 0) {
System.arraycopy(oldranges, cur, yranges, cur+2, rem);
System.arraycopy(oldcounts, cur/2,
crosscounts, cur/2+1,
rem/2);
}
yranges[cur+0] = lo;
yranges[cur+1] = hi;
crosscounts[cur/2] = dir;
limit += 2;
}
public void record(double ystart, double yend, int direction) {
if (ystart >= yend) {
return;
}
int cur = 0;
// Quickly jump over all pairs that are completely "above"
while (cur < limit && ystart > yranges[cur+1]) {
cur += 2;
}
if (cur < limit) {
int rdir = crosscounts[cur/2];
double yrlo = yranges[cur+0];
double yrhi = yranges[cur+1];
if (yrhi == ystart && rdir == direction) {
// Remove the range from the list and collapse it
// into the range being inserted. Note that the
// new combined range may overlap the following range
// so we must not simply combine the ranges in place
// unless we are at the last range.
if (cur+2 == limit) {
yranges[cur+1] = yend;
return;
}
remove(cur);
ystart = yrlo;
rdir = crosscounts[cur/2];
yrlo = yranges[cur+0];
yrhi = yranges[cur+1];
}
if (yend < yrlo) {
// Just insert the new range at the current location
insert(cur, ystart, yend, direction);
return;
}
if (yend == yrlo && rdir == direction) {
// Just prepend the new range to the current one
yranges[cur] = ystart;
return;
}
// The ranges must overlap - (yend > yrlo && yrhi > ystart)
if (ystart < yrlo) {
insert(cur, ystart, yrlo, direction);
cur += 2;
ystart = yrlo;
} else if (yrlo < ystart) {
insert(cur, yrlo, ystart, rdir);
cur += 2;
yrlo = ystart;
}
// assert(yrlo == ystart);
int newdir = rdir + direction;
double newend = Math.min(yend, yrhi);
if (newdir == 0) {
remove(cur);
} else {
crosscounts[cur/2] = newdir;
yranges[cur++] = ystart;
yranges[cur++] = newend;
}
ystart = yrlo = newend;
if (yrlo < yrhi) {
insert(cur, yrlo, yrhi, rdir);
}
}
if (ystart < yend) {
insert(cur, ystart, yend, direction);
}
}
}
}
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