| /* |
| * Copyright (c) 2007, 2017, 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 |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package sun.java2d.marlin; |
| |
| final class Curve { |
| |
| float ax, ay, bx, by, cx, cy, dx, dy; |
| float dax, day, dbx, dby; |
| |
| Curve() { |
| } |
| |
| void set(float[] points, int type) { |
| switch(type) { |
| case 8: |
| set(points[0], points[1], |
| points[2], points[3], |
| points[4], points[5], |
| points[6], points[7]); |
| return; |
| case 6: |
| set(points[0], points[1], |
| points[2], points[3], |
| points[4], points[5]); |
| return; |
| default: |
| throw new InternalError("Curves can only be cubic or quadratic"); |
| } |
| } |
| |
| void set(float x1, float y1, |
| float x2, float y2, |
| float x3, float y3, |
| float x4, float y4) |
| { |
| ax = 3.0f * (x2 - x3) + x4 - x1; |
| ay = 3.0f * (y2 - y3) + y4 - y1; |
| bx = 3.0f * (x1 - 2.0f * x2 + x3); |
| by = 3.0f * (y1 - 2.0f * y2 + y3); |
| cx = 3.0f * (x2 - x1); |
| cy = 3.0f * (y2 - y1); |
| dx = x1; |
| dy = y1; |
| dax = 3.0f * ax; day = 3.0f * ay; |
| dbx = 2.0f * bx; dby = 2.0f * by; |
| } |
| |
| void set(float x1, float y1, |
| float x2, float y2, |
| float x3, float y3) |
| { |
| ax = 0.0f; ay = 0.0f; |
| bx = x1 - 2.0f * x2 + x3; |
| by = y1 - 2.0f * y2 + y3; |
| cx = 2.0f * (x2 - x1); |
| cy = 2.0f * (y2 - y1); |
| dx = x1; |
| dy = y1; |
| dax = 0.0f; day = 0.0f; |
| dbx = 2.0f * bx; dby = 2.0f * by; |
| } |
| |
| float xat(float t) { |
| return t * (t * (t * ax + bx) + cx) + dx; |
| } |
| float yat(float t) { |
| return t * (t * (t * ay + by) + cy) + dy; |
| } |
| |
| float dxat(float t) { |
| return t * (t * dax + dbx) + cx; |
| } |
| |
| float dyat(float t) { |
| return t * (t * day + dby) + cy; |
| } |
| |
| int dxRoots(float[] roots, int off) { |
| return Helpers.quadraticRoots(dax, dbx, cx, roots, off); |
| } |
| |
| int dyRoots(float[] roots, int off) { |
| return Helpers.quadraticRoots(day, dby, cy, roots, off); |
| } |
| |
| int infPoints(float[] pts, int off) { |
| // inflection point at t if -f'(t)x*f''(t)y + f'(t)y*f''(t)x == 0 |
| // Fortunately, this turns out to be quadratic, so there are at |
| // most 2 inflection points. |
| final float a = dax * dby - dbx * day; |
| final float b = 2.0f * (cy * dax - day * cx); |
| final float c = cy * dbx - cx * dby; |
| |
| return Helpers.quadraticRoots(a, b, c, pts, off); |
| } |
| |
| // finds points where the first and second derivative are |
| // perpendicular. This happens when g(t) = f'(t)*f''(t) == 0 (where |
| // * is a dot product). Unfortunately, we have to solve a cubic. |
| private int perpendiculardfddf(float[] pts, int off) { |
| assert pts.length >= off + 4; |
| |
| // these are the coefficients of some multiple of g(t) (not g(t), |
| // because the roots of a polynomial are not changed after multiplication |
| // by a constant, and this way we save a few multiplications). |
| final float a = 2.0f * (dax*dax + day*day); |
| final float b = 3.0f * (dax*dbx + day*dby); |
| final float c = 2.0f * (dax*cx + day*cy) + dbx*dbx + dby*dby; |
| final float d = dbx*cx + dby*cy; |
| return Helpers.cubicRootsInAB(a, b, c, d, pts, off, 0.0f, 1.0f); |
| } |
| |
| // Tries to find the roots of the function ROC(t)-w in [0, 1). It uses |
| // a variant of the false position algorithm to find the roots. False |
| // position requires that 2 initial values x0,x1 be given, and that the |
| // function must have opposite signs at those values. To find such |
| // values, we need the local extrema of the ROC function, for which we |
| // need the roots of its derivative; however, it's harder to find the |
| // roots of the derivative in this case than it is to find the roots |
| // of the original function. So, we find all points where this curve's |
| // first and second derivative are perpendicular, and we pretend these |
| // are our local extrema. There are at most 3 of these, so we will check |
| // at most 4 sub-intervals of (0,1). ROC has asymptotes at inflection |
| // points, so roc-w can have at least 6 roots. This shouldn't be a |
| // problem for what we're trying to do (draw a nice looking curve). |
| int rootsOfROCMinusW(float[] roots, int off, final float w, final float err) { |
| // no OOB exception, because by now off<=6, and roots.length >= 10 |
| assert off <= 6 && roots.length >= 10; |
| int ret = off; |
| int numPerpdfddf = perpendiculardfddf(roots, off); |
| float t0 = 0.0f, ft0 = ROCsq(t0) - w*w; |
| roots[off + numPerpdfddf] = 1.0f; // always check interval end points |
| numPerpdfddf++; |
| for (int i = off; i < off + numPerpdfddf; i++) { |
| float t1 = roots[i], ft1 = ROCsq(t1) - w*w; |
| if (ft0 == 0.0f) { |
| roots[ret++] = t0; |
| } else if (ft1 * ft0 < 0.0f) { // have opposite signs |
| // (ROC(t)^2 == w^2) == (ROC(t) == w) is true because |
| // ROC(t) >= 0 for all t. |
| roots[ret++] = falsePositionROCsqMinusX(t0, t1, w*w, err); |
| } |
| t0 = t1; |
| ft0 = ft1; |
| } |
| |
| return ret - off; |
| } |
| |
| private static float eliminateInf(float x) { |
| return (x == Float.POSITIVE_INFINITY ? Float.MAX_VALUE : |
| (x == Float.NEGATIVE_INFINITY ? Float.MIN_VALUE : x)); |
| } |
| |
| // A slight modification of the false position algorithm on wikipedia. |
| // This only works for the ROCsq-x functions. It might be nice to have |
| // the function as an argument, but that would be awkward in java6. |
| // TODO: It is something to consider for java8 (or whenever lambda |
| // expressions make it into the language), depending on how closures |
| // and turn out. Same goes for the newton's method |
| // algorithm in Helpers.java |
| private float falsePositionROCsqMinusX(float x0, float x1, |
| final float x, final float err) |
| { |
| final int iterLimit = 100; |
| int side = 0; |
| float t = x1, ft = eliminateInf(ROCsq(t) - x); |
| float s = x0, fs = eliminateInf(ROCsq(s) - x); |
| float r = s, fr; |
| for (int i = 0; i < iterLimit && Math.abs(t - s) > err * Math.abs(t + s); i++) { |
| r = (fs * t - ft * s) / (fs - ft); |
| fr = ROCsq(r) - x; |
| if (sameSign(fr, ft)) { |
| ft = fr; t = r; |
| if (side < 0) { |
| fs /= (1 << (-side)); |
| side--; |
| } else { |
| side = -1; |
| } |
| } else if (fr * fs > 0) { |
| fs = fr; s = r; |
| if (side > 0) { |
| ft /= (1 << side); |
| side++; |
| } else { |
| side = 1; |
| } |
| } else { |
| break; |
| } |
| } |
| return r; |
| } |
| |
| private static boolean sameSign(float x, float y) { |
| // another way is to test if x*y > 0. This is bad for small x, y. |
| return (x < 0.0f && y < 0.0f) || (x > 0.0f && y > 0.0f); |
| } |
| |
| // returns the radius of curvature squared at t of this curve |
| // see http://en.wikipedia.org/wiki/Radius_of_curvature_(applications) |
| private float ROCsq(final float t) { |
| // dx=xat(t) and dy=yat(t). These calls have been inlined for efficiency |
| final float dx = t * (t * dax + dbx) + cx; |
| final float dy = t * (t * day + dby) + cy; |
| final float ddx = 2.0f * dax * t + dbx; |
| final float ddy = 2.0f * day * t + dby; |
| final float dx2dy2 = dx*dx + dy*dy; |
| final float ddx2ddy2 = ddx*ddx + ddy*ddy; |
| final float ddxdxddydy = ddx*dx + ddy*dy; |
| return dx2dy2*((dx2dy2*dx2dy2) / (dx2dy2 * ddx2ddy2 - ddxdxddydy*ddxdxddydy)); |
| } |
| } |