mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 16:25:49 +08:00
405 lines
12 KiB
Go
405 lines
12 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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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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package ofdgo
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import (
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"fmt"
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"math"
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)
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// geometryPolyline 保存展开后的子路径，独立记录闭合状态
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type geometryPolyline struct {
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points []Point
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closed bool
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direction Point
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}
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// Stroke 将曲线、虚线及线帽连接转换为非零填充轮廓
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// 曲线按Tolerance展开，默认误差为0.001毫米，重叠轮廓保持同向绕数
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// 结果未做布尔整理，按非零规则填充，区域运算需能处理重叠子路径的后端
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// 入参: options 描边样式
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// 返回: GeometryPath 描边轮廓, error 无效参数或精度限制
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func (p GeometryPath) Stroke(options StrokeOptions) (GeometryPath, error) {
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if err := validateStroke(options); err != nil {
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return nil, err
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}
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if err := p.validate(); err != nil {
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return nil, err
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}
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if options.Width/2 == 0 {
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return nil, fmt.Errorf("stroke width precision exhausted")
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}
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dashes := append([]float64(nil), options.Dashes...)
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total := 0.0
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for _, d := range dashes {
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total += d
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}
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if !finite(total) {
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return nil, fmt.Errorf("stroke dash period overflow")
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}
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if total == 0 {
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dashes = nil
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} else {
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if len(dashes)%2 != 0 {
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dashes = append(dashes, dashes...)
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total *= 2
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if !finite(total) {
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return nil, fmt.Errorf("stroke dash period overflow")
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}
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}
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}
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tolerance := options.Tolerance
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if tolerance == 0 {
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tolerance = .001
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}
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lines, err := p.strokePolylines(tolerance / 2)
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if err != nil {
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return nil, err
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}
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var result GeometryPath
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for _, line := range lines {
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parts := []geometryPolyline{line}
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if len(dashes) != 0 {
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parts, err = line.dash(dashes, total, options.DashOffset)
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if err != nil {
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return nil, err
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}
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}
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for _, part := range parts {
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result, err = part.stroke(result, options)
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if err != nil {
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return nil, err
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}
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if len(result) > 1<<20 {
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return nil, fmt.Errorf("stroke outline limit exceeded")
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}
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}
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}
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if err := result.validate(); err != nil {
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return nil, err
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}
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return result, nil
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}
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// strokePolylines 自适应展开贝塞尔，弦长亏损同时约束虚线累计长度误差
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// 入参: tolerance 展开误差
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// 返回: []geometryPolyline 子路径, error 展开限制
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func (p GeometryPath) strokePolylines(tolerance float64) ([]geometryPolyline, error) {
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curves, err := p.Curves(tolerance / 2)
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if err != nil {
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return nil, err
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}
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var result []geometryPolyline
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var line geometryPolyline
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var current, start Point
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drawn := false
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flush := func() {
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if drawn {
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result = append(result, line)
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}
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line, drawn = geometryPolyline{}, false
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}
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count := 0
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var flatten func([]Point, float64, int) error
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flatten = func(points []Point, budget float64, depth int) error {
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first, last := points[0], points[len(points)-1]
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chord := math.Hypot(last.X-first.X, last.Y-first.Y)
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length, distance := 0.0, 0.0
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for i := 1; i < len(points); i++ {
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length += math.Hypot(points[i].X-points[i-1].X, points[i].Y-points[i-1].Y)
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if i == len(points)-1 {
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continue
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}
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if chord == 0 {
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distance = math.Max(distance, math.Hypot(points[i].X-first.X, points[i].Y-first.Y))
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} else {
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distance = math.Max(distance, math.Abs((points[i].X-first.X)*((last.Y-first.Y)/chord)-(points[i].Y-first.Y)*((last.X-first.X)/chord)))
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}
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}
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if !finite(length) || !finite(distance) {
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return fmt.Errorf("stroke curve overflow")
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}
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if distance <= tolerance && length-chord <= budget {
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if last != line.points[len(line.points)-1] {
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line.points = append(line.points, last)
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count++
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}
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if count > 1<<18 {
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return fmt.Errorf("stroke subdivision limit exceeded")
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}
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return nil
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}
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if depth == 24 {
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return fmt.Errorf("stroke curve tolerance cannot be met")
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}
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work := append([]Point(nil), points...)
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left, right := make([]Point, len(points)), make([]Point, len(points))
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for n := len(points); n > 0; n-- {
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left[len(points)-n], right[n-1] = work[0], work[n-1]
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for i := 0; i < n-1; i++ {
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work[i] = geometryLerp(work[i], work[i+1], .5)
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}
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}
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if err := flatten(left, budget/2, depth+1); err != nil {
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return err
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}
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return flatten(right, budget/2, depth+1)
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}
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for _, s := range curves {
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switch s.Verb {
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case GeometryMove:
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flush()
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current, start = s.End, s.End
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line.points = []Point{current}
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case GeometryClose:
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if drawn {
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if current != start {
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line.points = append(line.points, start)
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}
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line.closed = true
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}
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flush()
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current = start
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line.points = []Point{current}
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default:
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drawn = true
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points := []Point{current}
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if s.Verb == GeometryQuad || s.Verb == GeometryCubic {
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points = append(points, s.Control1)
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}
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if s.Verb == GeometryCubic {
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points = append(points, s.Control2)
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}
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points = append(points, s.End)
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if err := flatten(points, tolerance/float64(len(curves)), 0); err != nil {
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return nil, err
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}
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current = s.End
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}
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}
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flush()
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return result, nil
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}
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// dash 按子路径重置相位并合并跨闭合接缝的连续虚线
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// 入参: pattern 非负偶数虚线数组, total 周期, offset 偏移
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// 返回: []geometryPolyline 虚线段, error 长度或细分限制
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func (line geometryPolyline) dash(pattern []float64, total, offset float64) ([]geometryPolyline, error) {
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phase := math.Mod(offset, total)
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if phase < 0 {
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phase += total
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}
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index := 0
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for phase > 0 && phase >= pattern[index] {
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phase -= pattern[index]
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index = (index + 1) % len(pattern)
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}
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if len(line.points) == 1 {
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if index%2 == 0 {
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return []geometryPolyline{line}, nil
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}
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return nil, nil
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}
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remaining := pattern[index] - phase
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var result []geometryPolyline
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var run []Point
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var direction Point
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flush := func() {
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if len(run) != 0 {
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result = append(result, geometryPolyline{points: run, direction: direction})
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run = nil
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}
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}
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steps := 0
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for i := 1; i < len(line.points); i++ {
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a, b := line.points[i-1], line.points[i]
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length := math.Hypot(b.X-a.X, b.Y-a.Y)
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if !finite(length) {
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return nil, fmt.Errorf("stroke dash length overflow")
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}
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for at := 0.0; ; {
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for remaining == 0 {
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steps++
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if steps > 1<<18 {
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return nil, fmt.Errorf("stroke dash subdivision limit exceeded")
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}
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if pattern[index] == 0 && index%2 == 0 && len(run) == 0 {
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result = append(result, geometryPolyline{points: []Point{geometryLerp(a, b, at/length)}, direction: Point{(b.X - a.X) / length, (b.Y - a.Y) / length}})
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}
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index = (index + 1) % len(pattern)
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remaining = pattern[index]
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if index%2 == 1 && remaining > 0 {
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flush()
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}
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}
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if at == length {
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break
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}
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step := math.Min(remaining, length-at)
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if at+step == at || steps > 1<<18 {
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return nil, fmt.Errorf("stroke dash subdivision limit exceeded")
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}
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steps++
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if index%2 == 0 {
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if len(run) == 0 {
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run = append(run, geometryLerp(a, b, at/length))
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direction = Point{(b.X - a.X) / length, (b.Y - a.Y) / length}
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}
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end := geometryLerp(a, b, (at+step)/length)
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if end != run[len(run)-1] {
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run = append(run, end)
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}
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}
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at += step
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remaining -= step
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}
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}
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flush()
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if line.closed && len(result) > 0 {
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first, last := &result[0], &result[len(result)-1]
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if first.points[0] == line.points[0] && last.points[len(last.points)-1] == line.points[0] {
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if len(result) == 1 {
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first.closed = len(first.points) > 1
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} else {
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first.points = append(last.points[:len(last.points)-1], first.points...)
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result = result[:len(result)-1]
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}
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}
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}
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return result, nil
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}
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// stroke 追加同向矩形、连接楔形及圆盘组成的非零填充区域
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// 入参: result 已有轮廓, options 描边样式
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// 返回: GeometryPath 填充轮廓, error 不支持的退化方形线帽
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func (line geometryPolyline) stroke(result GeometryPath, options StrokeOptions) (GeometryPath, error) {
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half := options.Width / 2
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polygon := func(points ...Point) {
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scale := 0.0
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for _, p := range points {
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scale = math.Max(scale, math.Max(math.Abs(p.X-points[0].X), math.Abs(p.Y-points[0].Y)))
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}
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if scale == 0 {
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return
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}
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area := 0.0
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for i, p := range points {
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q := points[(i+1)%len(points)]
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area += ((p.X-points[0].X)/scale)*((q.Y-points[0].Y)/scale) - ((p.Y-points[0].Y)/scale)*((q.X-points[0].X)/scale)
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}
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if area == 0 {
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return
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}
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if area < 0 {
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for i, j := 0, len(points)-1; i < j; i, j = i+1, j-1 {
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points[i], points[j] = points[j], points[i]
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}
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}
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result = append(result, GeometrySegment{Verb: GeometryMove, End: points[0]})
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for _, p := range points[1:] {
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result = append(result, GeometrySegment{Verb: GeometryLine, End: p})
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}
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result = append(result, GeometrySegment{Verb: GeometryClose})
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}
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disk := func(p Point) {
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result = append(result, GeometrySegment{Verb: GeometryMove, End: Point{p.X + half, p.Y}},
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GeometrySegment{Verb: GeometryArc, RadiusX: half, RadiusY: half, Sweep: true, End: Point{p.X - half, p.Y}},
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GeometrySegment{Verb: GeometryArc, RadiusX: half, RadiusY: half, Sweep: true, End: Point{p.X + half, p.Y}},
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GeometrySegment{Verb: GeometryClose})
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}
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points := line.points
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if len(points) == 1 {
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if line.closed {
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return nil, fmt.Errorf("directionless closed stroke: %w", ErrBackendUnavailable)
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}
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if options.Cap == "Round" {
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disk(points[0])
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} else if options.Cap == "Square" {
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d := line.direction
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if d == (Point{}) {
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return nil, fmt.Errorf("directionless square stroke cap: %w", ErrBackendUnavailable)
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}
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p := points[0]
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u, v := Point{d.X * half, d.Y * half}, Point{-d.Y * half, d.X * half}
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polygon(Point{p.X - u.X - v.X, p.Y - u.Y - v.Y}, Point{p.X + u.X - v.X, p.Y + u.Y - v.Y}, Point{p.X + u.X + v.X, p.Y + u.Y + v.Y}, Point{p.X - u.X + v.X, p.Y - u.Y + v.Y})
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}
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return result, nil
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}
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directions := make([]Point, len(points)-1)
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for i := range directions {
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a, b := points[i], points[i+1]
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length := math.Hypot(b.X-a.X, b.Y-a.Y)
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if length == 0 || !finite(length) {
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return nil, fmt.Errorf("invalid stroke segment length")
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}
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d := Point{(b.X - a.X) / length, (b.Y - a.Y) / length}
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directions[i] = d
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n := Point{-half * d.Y, half * d.X}
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polygon(Point{a.X + n.X, a.Y + n.Y}, Point{b.X + n.X, b.Y + n.Y}, Point{b.X - n.X, b.Y - n.Y}, Point{a.X - n.X, a.Y - n.Y})
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}
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join := func(p, a, b Point) {
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cross := a.X*b.Y - a.Y*b.X
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if cross == 0 {
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if options.Join == "Round" && a.X*b.X+a.Y*b.Y < 0 {
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disk(p)
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}
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return
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}
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side := -math.Copysign(half, cross)
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x := Point{p.X - side*a.Y, p.Y + side*a.X}
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y := Point{p.X - side*b.Y, p.Y + side*b.X}
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if options.Join == "Round" {
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if cross < 0 {
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x, y = y, x
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}
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result = append(result, GeometrySegment{Verb: GeometryMove, End: p},
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GeometrySegment{Verb: GeometryLine, End: x},
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GeometrySegment{Verb: GeometryArc, RadiusX: half, RadiusY: half, Sweep: true, End: y},
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GeometrySegment{Verb: GeometryClose})
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return
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}
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limit := options.MiterLimit
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if limit == 0 {
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limit = defaultMiterLimit
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}
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if options.Join == "" || options.Join == "Miter" {
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t := ((y.X-x.X)*b.Y - (y.Y-x.Y)*b.X) / cross
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m := Point{x.X + t*a.X, x.Y + t*a.Y}
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if math.Hypot(m.X-p.X, m.Y-p.Y) <= half*limit {
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polygon(p, x, m, y)
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return
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}
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}
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polygon(p, x, y)
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}
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for i := 1; i < len(points)-1; i++ {
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join(points[i], directions[i-1], directions[i])
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}
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if line.closed {
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join(points[0], directions[len(directions)-1], directions[0])
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} else {
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for _, end := range []struct{ p, d Point }{{points[0], Point{-directions[0].X, -directions[0].Y}}, {points[len(points)-1], directions[len(directions)-1]}} {
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if options.Cap == "Round" {
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disk(end.p)
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} else if options.Cap == "Square" {
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p, d := end.p, end.d
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n := Point{-half * d.Y, half * d.X}
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polygon(Point{p.X + n.X, p.Y + n.Y}, Point{p.X + n.X + half*d.X, p.Y + n.Y + half*d.Y}, Point{p.X - n.X + half*d.X, p.Y - n.Y + half*d.Y}, Point{p.X - n.X, p.Y - n.Y})
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}
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}
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}
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return result, nil
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}
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