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ab5c1bc441
Organize bezier functions for internal share. this bezier can be used in svg loader. Change-Id: I78acd3273c0528688ca46ff7c29d78607bd729bd
144 lines
4.5 KiB
C++
144 lines
4.5 KiB
C++
/*
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* Copyright (c) 2020 Samsung Electronics Co., Ltd All Rights Reserved
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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#ifndef _TVG_BEZIER_CPP_
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#define _TVG_BEZIER_CPP_
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#include "tvgCommon.h"
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/************************************************************************/
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/* Internal Class Implementation */
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/************************************************************************/
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static float _lineLength(const Point& pt1, const Point& pt2)
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{
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/* approximate sqrt(x*x + y*y) using alpha max plus beta min algorithm.
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With alpha = 1, beta = 3/8, giving results with the largest error less
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than 7% compared to the exact value. */
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Point diff = {pt2.x - pt1.x, pt2.y - pt1.y};
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if (diff.x < 0) diff.x = -diff.x;
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if (diff.y < 0) diff.y = -diff.y;
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return (diff.x > diff.y) ? (diff.x + diff.y * 0.375f) : (diff.y + diff.x * 0.375f);
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}
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/************************************************************************/
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/* External Class Implementation */
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/************************************************************************/
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namespace tvg
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{
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void bezSplit(const Bezier&cur, Bezier& left, Bezier& right)
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{
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auto c = (cur.ctrl1.x + cur.ctrl2.x) * 0.5f;
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left.ctrl1.x = (cur.start.x + cur.ctrl1.x) * 0.5f;
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right.ctrl2.x = (cur.ctrl2.x + cur.end.x) * 0.5f;
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left.start.x = cur.start.x;
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right.end.x = cur.end.x;
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left.ctrl2.x = (left.ctrl1.x + c) * 0.5f;
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right.ctrl1.x = (right.ctrl2.x + c) * 0.5f;
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left.end.x = right.start.x = (left.ctrl2.x + right.ctrl1.x) * 0.5f;
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c = (cur.ctrl1.y + cur.ctrl2.y) * 0.5f;
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left.ctrl1.y = (cur.start.y + cur.ctrl1.y) * 0.5f;
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right.ctrl2.y = (cur.ctrl2.y + cur.end.y) * 0.5f;
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left.start.y = cur.start.y;
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right.end.y = cur.end.y;
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left.ctrl2.y = (left.ctrl1.y + c) * 0.5f;
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right.ctrl1.y = (right.ctrl2.y + c) * 0.5f;
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left.end.y = right.start.y = (left.ctrl2.y + right.ctrl1.y) * 0.5f;
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}
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float bezLength(const Bezier& cur)
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{
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Bezier left, right;
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auto len = _lineLength(cur.start, cur.ctrl1) + _lineLength(cur.ctrl1, cur.ctrl2) + _lineLength(cur.ctrl2, cur.end);
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auto chord = _lineLength(cur.start, cur.end);
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if (fabs(len - chord) > FLT_EPSILON) {
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bezSplit(cur, left, right);
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return bezLength(left) + bezLength(right);
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}
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return len;
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}
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void bezSplitLeft(Bezier& cur, float at, Bezier& left)
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{
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left.start = cur.start;
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left.ctrl1.x = cur.start.x + at * (cur.ctrl1.x - cur.start.x);
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left.ctrl1.y = cur.start.y + at * (cur.ctrl1.y - cur.start.y);
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left.ctrl2.x = cur.ctrl1.x + at * (cur.ctrl2.x - cur.ctrl1.x); // temporary holding spot
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left.ctrl2.y = cur.ctrl1.y + at * (cur.ctrl2.y - cur.ctrl1.y); // temporary holding spot
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cur.ctrl2.x = cur.ctrl2.x + at * (cur.end.x - cur.ctrl2.x);
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cur.ctrl2.y = cur.ctrl2.y + at * (cur.end.y - cur.ctrl2.y);
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cur.ctrl1.x = left.ctrl2.x + at * (cur.ctrl2.x - left.ctrl2.x);
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cur.ctrl1.y = left.ctrl2.y + at * (cur.ctrl2.y - left.ctrl2.y);
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left.ctrl2.x = left.ctrl1.x + at * (left.ctrl2.x - left.ctrl1.x);
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left.ctrl2.y = left.ctrl1.y + at * (left.ctrl2.y - left.ctrl1.y);
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left.end.x = cur.start.x = left.ctrl2.x + at * (cur.ctrl1.x - left.ctrl2.x);
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left.end.y = cur.start.y = left.ctrl2.y + at * (cur.ctrl1.y - left.ctrl2.y);
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}
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float bezAt(const Bezier& bz, float at)
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{
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auto len = bezLength(bz);
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auto biggest = 1.0f;
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if (at >= len) return 1.0f;
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at *= 0.5f;
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while (true) {
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auto right = bz;
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Bezier left;
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bezSplitLeft(right, at, left);
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auto len2 = bezLength(left);
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if (fabs(len2 - len) < FLT_EPSILON) break;
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if (len2 < len) {
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at += (biggest - at) * 0.5f;
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} else {
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biggest = at;
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at -= (at * 0.5f);
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}
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}
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return at;
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}
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void bezSplitAt(const Bezier& cur, float at, Bezier& left, Bezier& right)
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{
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right = cur;
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auto t = bezAt(right, at);
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bezSplitLeft(right, t, left);
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}
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}
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#endif //_TVG_BEZIER_CPP_
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