/*
* Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
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*/
package java.awt.geom;
import java.util.*;
/**
* A utility class to iterate over the path segments of an arc
* through the PathIterator interface.
*
* @author Jim Graham
*/
class
ArcIterator implements
PathIterator {
double
x,
y,
w,
h,
angStRad,
increment,
cv;
AffineTransform affine;
int
index;
int
arcSegs;
int
lineSegs;
ArcIterator(
Arc2D a,
AffineTransform at) {
this.
w =
a.
getWidth() / 2;
this.
h =
a.
getHeight() / 2;
this.
x =
a.
getX() +
w;
this.
y =
a.
getY() +
h;
this.
angStRad = -
Math.
toRadians(
a.
getAngleStart());
this.
affine =
at;
double
ext = -
a.
getAngleExtent();
if (
ext >= 360.0 ||
ext <= -360) {
arcSegs = 4;
this.
increment =
Math.
PI / 2;
// btan(Math.PI / 2);
this.
cv = 0.5522847498307933;
if (
ext < 0) {
increment = -
increment;
cv = -
cv;
}
} else {
arcSegs = (int)
Math.
ceil(
Math.
abs(
ext) / 90.0);
this.
increment =
Math.
toRadians(
ext /
arcSegs);
this.
cv =
btan(
increment);
if (
cv == 0) {
arcSegs = 0;
}
}
switch (
a.
getArcType()) {
case
Arc2D.
OPEN:
lineSegs = 0;
break;
case
Arc2D.
CHORD:
lineSegs = 1;
break;
case
Arc2D.
PIE:
lineSegs = 2;
break;
}
if (
w < 0 ||
h < 0) {
arcSegs =
lineSegs = -1;
}
}
/**
* Return the winding rule for determining the insideness of the
* path.
* @see #WIND_EVEN_ODD
* @see #WIND_NON_ZERO
*/
public int
getWindingRule() {
return
WIND_NON_ZERO;
}
/**
* Tests if there are more points to read.
* @return true if there are more points to read
*/
public boolean
isDone() {
return
index >
arcSegs +
lineSegs;
}
/**
* Moves the iterator to the next segment of the path forwards
* along the primary direction of traversal as long as there are
* more points in that direction.
*/
public void
next() {
index++;
}
/*
* btan computes the length (k) of the control segments at
* the beginning and end of a cubic bezier that approximates
* a segment of an arc with extent less than or equal to
* 90 degrees. This length (k) will be used to generate the
* 2 bezier control points for such a segment.
*
* Assumptions:
* a) arc is centered on 0,0 with radius of 1.0
* b) arc extent is less than 90 degrees
* c) control points should preserve tangent
* d) control segments should have equal length
*
* Initial data:
* start angle: ang1
* end angle: ang2 = ang1 + extent
* start point: P1 = (x1, y1) = (cos(ang1), sin(ang1))
* end point: P4 = (x4, y4) = (cos(ang2), sin(ang2))
*
* Control points:
* P2 = (x2, y2)
* | x2 = x1 - k * sin(ang1) = cos(ang1) - k * sin(ang1)
* | y2 = y1 + k * cos(ang1) = sin(ang1) + k * cos(ang1)
*
* P3 = (x3, y3)
* | x3 = x4 + k * sin(ang2) = cos(ang2) + k * sin(ang2)
* | y3 = y4 - k * cos(ang2) = sin(ang2) - k * cos(ang2)
*
* The formula for this length (k) can be found using the
* following derivations:
*
* Midpoints:
* a) bezier (t = 1/2)
* bPm = P1 * (1-t)^3 +
* 3 * P2 * t * (1-t)^2 +
* 3 * P3 * t^2 * (1-t) +
* P4 * t^3 =
* = (P1 + 3P2 + 3P3 + P4)/8
*
* b) arc
* aPm = (cos((ang1 + ang2)/2), sin((ang1 + ang2)/2))
*
* Let angb = (ang2 - ang1)/2; angb is half of the angle
* between ang1 and ang2.
*
* Solve the equation bPm == aPm
*
* a) For xm coord:
* x1 + 3*x2 + 3*x3 + x4 = 8*cos((ang1 + ang2)/2)
*
* cos(ang1) + 3*cos(ang1) - 3*k*sin(ang1) +
* 3*cos(ang2) + 3*k*sin(ang2) + cos(ang2) =
* = 8*cos((ang1 + ang2)/2)
*
* 4*cos(ang1) + 4*cos(ang2) + 3*k*(sin(ang2) - sin(ang1)) =
* = 8*cos((ang1 + ang2)/2)
*
* 8*cos((ang1 + ang2)/2)*cos((ang2 - ang1)/2) +
* 6*k*sin((ang2 - ang1)/2)*cos((ang1 + ang2)/2) =
* = 8*cos((ang1 + ang2)/2)
*
* 4*cos(angb) + 3*k*sin(angb) = 4
*
* k = 4 / 3 * (1 - cos(angb)) / sin(angb)
*
* b) For ym coord we derive the same formula.
*
* Since this formula can generate "NaN" values for small
* angles, we will derive a safer form that does not involve
* dividing by very small values:
* (1 - cos(angb)) / sin(angb) =
* = (1 - cos(angb))*(1 + cos(angb)) / sin(angb)*(1 + cos(angb)) =
* = (1 - cos(angb)^2) / sin(angb)*(1 + cos(angb)) =
* = sin(angb)^2 / sin(angb)*(1 + cos(angb)) =
* = sin(angb) / (1 + cos(angb))
*
*/
private static double
btan(double
increment) {
increment /= 2.0;
return 4.0 / 3.0 *
Math.
sin(
increment) / (1.0 +
Math.
cos(
increment));
}
/**
* Returns the coordinates and type of the current path segment in
* the iteration.
* The return value is the path segment type:
* SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
* A float array of length 6 must be passed in and may be used to
* store the coordinates of the point(s).
* Each point is stored as a pair of float x,y coordinates.
* SEG_MOVETO and SEG_LINETO types will return one point,
* SEG_QUADTO will return two points,
* SEG_CUBICTO will return 3 points
* and SEG_CLOSE will not return any points.
* @see #SEG_MOVETO
* @see #SEG_LINETO
* @see #SEG_QUADTO
* @see #SEG_CUBICTO
* @see #SEG_CLOSE
*/
public int
currentSegment(float[]
coords) {
if (
isDone()) {
throw new
NoSuchElementException("arc iterator out of bounds");
}
double
angle =
angStRad;
if (
index == 0) {
coords[0] = (float) (
x +
Math.
cos(
angle) *
w);
coords[1] = (float) (
y +
Math.
sin(
angle) *
h);
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 1);
}
return
SEG_MOVETO;
}
if (
index >
arcSegs) {
if (
index ==
arcSegs +
lineSegs) {
return
SEG_CLOSE;
}
coords[0] = (float)
x;
coords[1] = (float)
y;
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 1);
}
return
SEG_LINETO;
}
angle +=
increment * (
index - 1);
double
relx =
Math.
cos(
angle);
double
rely =
Math.
sin(
angle);
coords[0] = (float) (
x + (
relx -
cv *
rely) *
w);
coords[1] = (float) (
y + (
rely +
cv *
relx) *
h);
angle +=
increment;
relx =
Math.
cos(
angle);
rely =
Math.
sin(
angle);
coords[2] = (float) (
x + (
relx +
cv *
rely) *
w);
coords[3] = (float) (
y + (
rely -
cv *
relx) *
h);
coords[4] = (float) (
x +
relx *
w);
coords[5] = (float) (
y +
rely *
h);
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 3);
}
return
SEG_CUBICTO;
}
/**
* Returns the coordinates and type of the current path segment in
* the iteration.
* The return value is the path segment type:
* SEG_MOVETO, SEG_LINETO, SEG_QUADTO, SEG_CUBICTO, or SEG_CLOSE.
* A double array of length 6 must be passed in and may be used to
* store the coordinates of the point(s).
* Each point is stored as a pair of double x,y coordinates.
* SEG_MOVETO and SEG_LINETO types will return one point,
* SEG_QUADTO will return two points,
* SEG_CUBICTO will return 3 points
* and SEG_CLOSE will not return any points.
* @see #SEG_MOVETO
* @see #SEG_LINETO
* @see #SEG_QUADTO
* @see #SEG_CUBICTO
* @see #SEG_CLOSE
*/
public int
currentSegment(double[]
coords) {
if (
isDone()) {
throw new
NoSuchElementException("arc iterator out of bounds");
}
double
angle =
angStRad;
if (
index == 0) {
coords[0] =
x +
Math.
cos(
angle) *
w;
coords[1] =
y +
Math.
sin(
angle) *
h;
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 1);
}
return
SEG_MOVETO;
}
if (
index >
arcSegs) {
if (
index ==
arcSegs +
lineSegs) {
return
SEG_CLOSE;
}
coords[0] =
x;
coords[1] =
y;
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 1);
}
return
SEG_LINETO;
}
angle +=
increment * (
index - 1);
double
relx =
Math.
cos(
angle);
double
rely =
Math.
sin(
angle);
coords[0] =
x + (
relx -
cv *
rely) *
w;
coords[1] =
y + (
rely +
cv *
relx) *
h;
angle +=
increment;
relx =
Math.
cos(
angle);
rely =
Math.
sin(
angle);
coords[2] =
x + (
relx +
cv *
rely) *
w;
coords[3] =
y + (
rely -
cv *
relx) *
h;
coords[4] =
x +
relx *
w;
coords[5] =
y +
rely *
h;
if (
affine != null) {
affine.
transform(
coords, 0,
coords, 0, 3);
}
return
SEG_CUBICTO;
}
}