/*
* Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
* 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.java2d.pisces;
import java.util.Arrays;
final class Helpers {
private Helpers() {
throw new Error("This is a non instantiable class");
}
static boolean within(final float x, final float y, final float err) {
final float d = y - x;
return (d <= err && d >= -err);
}
static boolean within(final double x, final double y, final double err) {
final double d = y - x;
return (d <= err && d >= -err);
}
static int quadraticRoots(final float a, final float b,
final float c, float[] zeroes, final int off)
{
int ret = off;
float t;
if (a != 0f) {
final float dis = b*b - 4*a*c;
if (dis > 0) {
final float sqrtDis = (float)Math.sqrt(dis);
// depending on the sign of b we use a slightly different
// algorithm than the traditional one to find one of the roots
// so we can avoid adding numbers of different signs (which
// might result in loss of precision).
if (b >= 0) {
zeroes[ret++] = (2 * c) / (-b - sqrtDis);
zeroes[ret++] = (-b - sqrtDis) / (2 * a);
} else {
zeroes[ret++] = (-b + sqrtDis) / (2 * a);
zeroes[ret++] = (2 * c) / (-b + sqrtDis);
}
} else if (dis == 0f) {
t = (-b) / (2 * a);
zeroes[ret++] = t;
}
} else {
if (b != 0f) {
t = (-c) / b;
zeroes[ret++] = t;
}
}
return ret - off;
}
// find the roots of g(t) = a*t^3 + b*t^2 + c*t + d in [A,B)
// We will not use Cardano's method, since it is complicated and
// involves too many square and cubic roots. We will use Newton's method.
// TODO: this should probably return ALL roots. Then the user can do
// his own filtering of roots outside [A,B).
static int cubicRootsInAB(final float a, final float b,
final float c, final float d,
float[] pts, final int off, final float E,
final float A, final float B)
{
if (a == 0) {
return quadraticRoots(b, c, d, pts, off);
}
// the coefficients of g'(t). no dc variable because dc=c
// we use these to get the critical points of g(t), which
// we then use to chose starting points for Newton's method. These
// should be very close to the actual roots.
final float da = 3 * a;
final float db = 2 * b;
int numCritPts = quadraticRoots(da, db, c, pts, off+1);
numCritPts = filterOutNotInAB(pts, off+1, numCritPts, A, B) - off - 1;
// need them sorted.
if (numCritPts == 2 && pts[off+1] > pts[off+2]) {
float tmp = pts[off+1];
pts[off+1] = pts[off+2];
pts[off+2] = tmp;
}
int ret = off;
// we don't actually care much about the extrema themselves. We
// only use them to ensure that g(t) is monotonic in each
// interval [pts[i],pts[i+1] (for i in off...off+numCritPts+1).
// This will allow us to determine intervals containing exactly
// one root.
// The end points of the interval are always local extrema.
pts[off] = A;
pts[off + numCritPts + 1] = B;
numCritPts += 2;
float x0 = pts[off], fx0 = evalCubic(a, b, c, d, x0);
for (int i = off; i < off + numCritPts - 1; i++) {
float x1 = pts[i+1], fx1 = evalCubic(a, b, c, d, x1);
if (fx0 == 0f) {
pts[ret++] = x0;
} else if (fx1 * fx0 < 0f) { // have opposite signs
pts[ret++] = CubicNewton(a, b, c, d,
x0 + fx0 * (x1 - x0) / (fx0 - fx1), E);
}
x0 = x1;
fx0 = fx1;
}
return ret - off;
}
// precondition: the polynomial to be evaluated must not be 0 at x0.
static float CubicNewton(final float a, final float b,
final float c, final float d,
float x0, final float err)
{
// considering how this function is used, 10 should be more than enough
final int itlimit = 10;
float fx0 = evalCubic(a, b, c, d, x0);
float x1;
int count = 0;
while(true) {
x1 = x0 - (fx0 / evalCubic(0, 3 * a, 2 * b, c, x0));
if (Math.abs(x1 - x0) < err * Math.abs(x1 + x0) || count == itlimit) {
break;
}
x0 = x1;
fx0 = evalCubic(a, b, c, d, x0);
count++;
}
return x1;
}
// fills the input array with numbers 0, INC, 2*INC, ...
static void fillWithIdxes(final float[] data, final int[] idxes) {
if (idxes.length > 0) {
idxes[0] = 0;
for (int i = 1; i < idxes.length; i++) {
idxes[i] = idxes[i-1] + (int)data[idxes[i-1]];
}
}
}
static void fillWithIdxes(final int[] idxes, final int inc) {
if (idxes.length > 0) {
idxes[0] = 0;
for (int i = 1; i < idxes.length; i++) {
idxes[i] = idxes[i-1] + inc;
}
}
}
// These use a hardcoded factor of 2 for increasing sizes. Perhaps this
// should be provided as an argument.
static float[] widenArray(float[] in, final int cursize, final int numToAdd) {
if (in == null) {
return new float[5 * numToAdd];
}
if (in.length >= cursize + numToAdd) {
return in;
}
return Arrays.copyOf(in, 2 * (cursize + numToAdd));
}
static int[] widenArray(int[] in, final int cursize, final int numToAdd) {
if (in.length >= cursize + numToAdd) {
return in;
}
return Arrays.copyOf(in, 2 * (cursize + numToAdd));
}
static float evalCubic(final float a, final float b,
final float c, final float d,
final float t)
{
return t * (t * (t * a + b) + c) + d;
}
static float evalQuad(final float a, final float b,
final float c, final float t)
{
return t * (t * a + b) + c;
}
// returns the index 1 past the last valid element remaining after filtering
static int filterOutNotInAB(float[] nums, final int off, final int len,
final float a, final float b)
{
int ret = off;
for (int i = off; i < off + len; i++) {
if (nums[i] > a && nums[i] < b) {
nums[ret++] = nums[i];
}
}
return ret;
}
static float polyLineLength(float[] poly, final int off, final int nCoords) {
assert nCoords % 2 == 0 && poly.length >= off + nCoords : "";
float acc = 0;
for (int i = off + 2; i < off + nCoords; i += 2) {
acc += linelen(poly[i], poly[i+1], poly[i-2], poly[i-1]);
}
return acc;
}
static float linelen(float x1, float y1, float x2, float y2) {
return (float)Math.hypot(x2 - x1, y2 - y1);
}
static void subdivide(float[] src, int srcoff, float[] left, int leftoff,
float[] right, int rightoff, int type)
{
switch(type) {
case 6:
Helpers.subdivideQuad(src, srcoff, left, leftoff, right, rightoff);
break;
case 8:
Helpers.subdivideCubic(src, srcoff, left, leftoff, right, rightoff);
break;
default:
throw new InternalError("Unsupported curve type");
}
}
static void isort(float[] a, int off, int len) {
for (int i = off + 1; i < off + len; i++) {
float ai = a[i];
int j = i - 1;
for (; j >= off && a[j] > ai; j--) {
a[j+1] = a[j];
}
a[j+1] = ai;
}
}
// Most of these are copied from classes in java.awt.geom because we need
// float versions of these functions, and Line2D, CubicCurve2D,
// QuadCurve2D don't provide them.
/**
* Subdivides the cubic curve specified by the coordinates
* stored in the src
array at indices srcoff
* through (srcoff
+ 7) and stores the
* resulting two subdivided curves into the two result arrays at the
* corresponding indices.
* Either or both of the left
and right
* arrays may be null
or a reference to the same array
* as the src
array.
* Note that the last point in the first subdivided curve is the
* same as the first point in the second subdivided curve. Thus,
* it is possible to pass the same array for left
* and right
and to use offsets, such as rightoff
* equals (leftoff
+ 6), in order
* to avoid allocating extra storage for this common point.
* @param src the array holding the coordinates for the source curve
* @param srcoff the offset into the array of the beginning of the
* the 6 source coordinates
* @param left the array for storing the coordinates for the first
* half of the subdivided curve
* @param leftoff the offset into the array of the beginning of the
* the 6 left coordinates
* @param right the array for storing the coordinates for the second
* half of the subdivided curve
* @param rightoff the offset into the array of the beginning of the
* the 6 right coordinates
* @since 1.7
*/
static void subdivideCubic(float src[], int srcoff,
float left[], int leftoff,
float right[], int rightoff)
{
float x1 = src[srcoff + 0];
float y1 = src[srcoff + 1];
float ctrlx1 = src[srcoff + 2];
float ctrly1 = src[srcoff + 3];
float ctrlx2 = src[srcoff + 4];
float ctrly2 = src[srcoff + 5];
float x2 = src[srcoff + 6];
float y2 = src[srcoff + 7];
if (left != null) {
left[leftoff + 0] = x1;
left[leftoff + 1] = y1;
}
if (right != null) {
right[rightoff + 6] = x2;
right[rightoff + 7] = y2;
}
x1 = (x1 + ctrlx1) / 2.0f;
y1 = (y1 + ctrly1) / 2.0f;
x2 = (x2 + ctrlx2) / 2.0f;
y2 = (y2 + ctrly2) / 2.0f;
float centerx = (ctrlx1 + ctrlx2) / 2.0f;
float centery = (ctrly1 + ctrly2) / 2.0f;
ctrlx1 = (x1 + centerx) / 2.0f;
ctrly1 = (y1 + centery) / 2.0f;
ctrlx2 = (x2 + centerx) / 2.0f;
ctrly2 = (y2 + centery) / 2.0f;
centerx = (ctrlx1 + ctrlx2) / 2.0f;
centery = (ctrly1 + ctrly2) / 2.0f;
if (left != null) {
left[leftoff + 2] = x1;
left[leftoff + 3] = y1;
left[leftoff + 4] = ctrlx1;
left[leftoff + 5] = ctrly1;
left[leftoff + 6] = centerx;
left[leftoff + 7] = centery;
}
if (right != null) {
right[rightoff + 0] = centerx;
right[rightoff + 1] = centery;
right[rightoff + 2] = ctrlx2;
right[rightoff + 3] = ctrly2;
right[rightoff + 4] = x2;
right[rightoff + 5] = y2;
}
}
static void subdivideCubicAt(float t, float src[], int srcoff,
float left[], int leftoff,
float right[], int rightoff)
{
float x1 = src[srcoff + 0];
float y1 = src[srcoff + 1];
float ctrlx1 = src[srcoff + 2];
float ctrly1 = src[srcoff + 3];
float ctrlx2 = src[srcoff + 4];
float ctrly2 = src[srcoff + 5];
float x2 = src[srcoff + 6];
float y2 = src[srcoff + 7];
if (left != null) {
left[leftoff + 0] = x1;
left[leftoff + 1] = y1;
}
if (right != null) {
right[rightoff + 6] = x2;
right[rightoff + 7] = y2;
}
x1 = x1 + t * (ctrlx1 - x1);
y1 = y1 + t * (ctrly1 - y1);
x2 = ctrlx2 + t * (x2 - ctrlx2);
y2 = ctrly2 + t * (y2 - ctrly2);
float centerx = ctrlx1 + t * (ctrlx2 - ctrlx1);
float centery = ctrly1 + t * (ctrly2 - ctrly1);
ctrlx1 = x1 + t * (centerx - x1);
ctrly1 = y1 + t * (centery - y1);
ctrlx2 = centerx + t * (x2 - centerx);
ctrly2 = centery + t * (y2 - centery);
centerx = ctrlx1 + t * (ctrlx2 - ctrlx1);
centery = ctrly1 + t * (ctrly2 - ctrly1);
if (left != null) {
left[leftoff + 2] = x1;
left[leftoff + 3] = y1;
left[leftoff + 4] = ctrlx1;
left[leftoff + 5] = ctrly1;
left[leftoff + 6] = centerx;
left[leftoff + 7] = centery;
}
if (right != null) {
right[rightoff + 0] = centerx;
right[rightoff + 1] = centery;
right[rightoff + 2] = ctrlx2;
right[rightoff + 3] = ctrly2;
right[rightoff + 4] = x2;
right[rightoff + 5] = y2;
}
}
static void subdivideQuad(float src[], int srcoff,
float left[], int leftoff,
float right[], int rightoff)
{
float x1 = src[srcoff + 0];
float y1 = src[srcoff + 1];
float ctrlx = src[srcoff + 2];
float ctrly = src[srcoff + 3];
float x2 = src[srcoff + 4];
float y2 = src[srcoff + 5];
if (left != null) {
left[leftoff + 0] = x1;
left[leftoff + 1] = y1;
}
if (right != null) {
right[rightoff + 4] = x2;
right[rightoff + 5] = y2;
}
x1 = (x1 + ctrlx) / 2.0f;
y1 = (y1 + ctrly) / 2.0f;
x2 = (x2 + ctrlx) / 2.0f;
y2 = (y2 + ctrly) / 2.0f;
ctrlx = (x1 + x2) / 2.0f;
ctrly = (y1 + y2) / 2.0f;
if (left != null) {
left[leftoff + 2] = x1;
left[leftoff + 3] = y1;
left[leftoff + 4] = ctrlx;
left[leftoff + 5] = ctrly;
}
if (right != null) {
right[rightoff + 0] = ctrlx;
right[rightoff + 1] = ctrly;
right[rightoff + 2] = x2;
right[rightoff + 3] = y2;
}
}
static void subdivideQuadAt(float t, float src[], int srcoff,
float left[], int leftoff,
float right[], int rightoff)
{
float x1 = src[srcoff + 0];
float y1 = src[srcoff + 1];
float ctrlx = src[srcoff + 2];
float ctrly = src[srcoff + 3];
float x2 = src[srcoff + 4];
float y2 = src[srcoff + 5];
if (left != null) {
left[leftoff + 0] = x1;
left[leftoff + 1] = y1;
}
if (right != null) {
right[rightoff + 4] = x2;
right[rightoff + 5] = y2;
}
x1 = x1 + t * (ctrlx - x1);
y1 = y1 + t * (ctrly - y1);
x2 = ctrlx + t * (x2 - ctrlx);
y2 = ctrly + t * (y2 - ctrly);
ctrlx = x1 + t * (x2 - x1);
ctrly = y1 + t * (y2 - y1);
if (left != null) {
left[leftoff + 2] = x1;
left[leftoff + 3] = y1;
left[leftoff + 4] = ctrlx;
left[leftoff + 5] = ctrly;
}
if (right != null) {
right[rightoff + 0] = ctrlx;
right[rightoff + 1] = ctrly;
right[rightoff + 2] = x2;
right[rightoff + 3] = y2;
}
}
static void subdivideAt(float t, float src[], int srcoff,
float left[], int leftoff,
float right[], int rightoff, int size)
{
switch(size) {
case 8:
subdivideCubicAt(t, src, srcoff, left, leftoff, right, rightoff);
break;
case 6:
subdivideQuadAt(t, src, srcoff, left, leftoff, right, rightoff);
break;
}
}
}