mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 14:31:12 +08:00
408 lines
12 KiB
Go
408 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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"context"
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"fmt"
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"math"
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"slices"
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"github.com/tdewolff/canvas"
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"github.com/xiaoqidun/pdfgo"
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)
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// PDF链接区域细分上限与曲线逼近误差，误差单位为毫米
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const (
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pdfLinkEdgeLimit = 4096
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pdfLinkQuadLimit = 65536
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pdfLinkTolerance = 0.01
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)
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// pdfLinkEdge 保存按纵坐标排序的边及原始绕行方向
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type pdfLinkEdge struct {
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a, b pdfgo.Point
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winding int
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}
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// pdfLinkCross 保存水平扫描线与区域边的交点
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type pdfLinkCross struct {
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x float64
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edge int
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}
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// pdfActionRegion 将非零绕行区域分解为PDF链接四边形，保留空洞和相交轮廓
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// 入参: ctx 取消上下文, outline 页面SVG路径, pageH 页面高度
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// 返回: *pdfgo.LinkRegion 链接区域，nil表示沿用矩形, error 解析或复杂度错误
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func pdfActionRegion(ctx context.Context, outline string, pageH float64) (*pdfgo.LinkRegion, error) {
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if outline == "" {
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return nil, nil
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}
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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path, err := canvas.ParseSVGPath(outline)
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if err != nil {
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return nil, err
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}
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if path.Len() > pdfLinkEdgeLimit {
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return nil, fmt.Errorf("PDF link region exceeds edge limit")
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}
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if _, ok := geometryRectangleBounds(*geometryFromCanvasPath(path)); ok {
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return nil, nil
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}
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path, err = flattenPDFLink(ctx, path)
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if err != nil {
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return nil, err
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}
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if quads := convexPDFLink(path, pageH); len(quads) != 0 {
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return pdfLinkRegionBounds(quads), nil
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}
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var edges []pdfLinkEdge
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var levels []float64
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var start, previous pdfgo.Point
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open := false
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add := func(a, b pdfgo.Point) {
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if a.Y == b.Y {
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return
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}
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edge := pdfLinkEdge{a: a, b: b, winding: 1}
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if a.Y > b.Y {
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edge.a, edge.b, edge.winding = b, a, -1
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}
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edges = append(edges, edge)
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levels = append(levels, edge.a.Y, edge.b.Y)
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}
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scanner := path.Scanner()
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for scanner.Scan() {
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p := scanner.End()
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point := pdfgo.Point{X: p.X * 72 / 25.4, Y: (pageH - p.Y) * 72 / 25.4}
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if !finite(point.X) || !finite(point.Y) {
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return nil, fmt.Errorf("invalid PDF link coordinate")
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}
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switch scanner.Cmd() {
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case canvas.MoveToCmd:
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if open {
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add(previous, start)
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}
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start, open = point, true
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case canvas.LineToCmd:
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if !open {
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start, open = previous, true
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}
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add(previous, point)
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case canvas.CloseCmd:
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add(previous, start)
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open = false
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}
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previous = point
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}
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if open {
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add(previous, start)
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}
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for i, a := range edges {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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for _, b := range edges[i+1:] {
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low, high := max(a.a.Y, b.a.Y), min(a.b.Y, b.b.Y)
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if low >= high {
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continue
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}
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d0, d1 := a.x(low)-b.x(low), a.x(high)-b.x(high)
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if d0 < 0 && d1 > 0 || d0 > 0 && d1 < 0 {
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y := low + (high-low)*(d0/(d0-d1))
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if !finite(y) {
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return nil, fmt.Errorf("invalid PDF link intersection")
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}
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levels = append(levels, y)
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if len(levels) > pdfLinkQuadLimit {
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return nil, fmt.Errorf("PDF link region exceeds intersection limit")
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}
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}
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}
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}
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slices.Sort(levels)
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levels = slices.Compact(levels)
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region := &pdfgo.LinkRegion{}
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crossings := make([]pdfLinkCross, 0, len(edges))
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for i := 1; i < len(levels); i++ {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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low, high := levels[i-1], levels[i]
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mid := low + (high-low)/2
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if mid <= low || mid >= high {
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continue
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}
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crossings = crossings[:0]
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for j, edge := range edges {
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if edge.a.Y < mid && mid < edge.b.Y {
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crossings = append(crossings, pdfLinkCross{edge.x(mid), j})
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}
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}
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slices.SortFunc(crossings, func(a, b pdfLinkCross) int {
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if a.x < b.x {
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return -1
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}
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if a.x > b.x {
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return 1
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}
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return a.edge - b.edge
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})
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winding, left := 0, 0
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for _, cross := range crossings {
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before := winding
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winding += edges[cross.edge].winding
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if before == 0 && winding != 0 {
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left = cross.edge
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}
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if before != 0 && winding == 0 {
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a, b := edges[left], edges[cross.edge]
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quad := [4]pdfgo.Point{{X: a.x(low), Y: low}, {X: b.x(low), Y: low}, {X: b.x(high), Y: high}, {X: a.x(high), Y: high}}
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region.Quads = appendPDFLinkQuad(region.Quads, quad)
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if len(region.Quads) > pdfLinkQuadLimit {
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return nil, fmt.Errorf("PDF link region exceeds quadrilateral limit")
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}
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}
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}
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}
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if len(region.Quads) == 0 {
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return region, nil
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}
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return pdfLinkRegionBounds(region.Quads), nil
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}
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// convexPDFLink 直接保留单个凸四边形，三角形只分成三个四边形
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// 入参: path 已展开路径, pageH 页面高度
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// 返回: [][4]pdfgo.Point 逆时针四边形，不适用时为空
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func convexPDFLink(path *canvas.Path, pageH float64) [][4]pdfgo.Point {
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if path.HasSubpaths() || path.Len() > 6 {
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return nil
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}
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points := path.Coords()
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if len(points) > 1 && points[0] == points[len(points)-1] {
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points = points[:len(points)-1]
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}
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if len(points) < 3 || len(points) > 4 {
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return nil
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}
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var storage [4]pdfgo.Point
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vertices := storage[:len(points)]
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for i, p := range points {
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vertices[i] = pdfgo.Point{X: p.X * 72 / 25.4, Y: (pageH - p.Y) * 72 / 25.4}
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}
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direction := 0.0
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for i, a := range vertices {
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b, c := vertices[(i+1)%len(vertices)], vertices[(i+2)%len(vertices)]
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cross := pdfLinkTurn(a, b, c)
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if !finite(cross) || cross == 0 || direction != 0 && (direction < 0) != (cross < 0) {
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return nil
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}
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direction = cross
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}
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if direction < 0 {
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slices.Reverse(vertices)
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}
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if len(vertices) == 4 {
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return [][4]pdfgo.Point{storage}
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}
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return appendPDFLinkTriangle(nil, [3]pdfgo.Point{vertices[0], vertices[1], vertices[2]})
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}
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// pdfLinkRegionBounds 计算四边形共同的注解矩形，保证全部顶点落在矩形内
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// 入参: quads 链接四边形
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// 返回: *pdfgo.LinkRegion 链接区域
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func pdfLinkRegionBounds(quads [][4]pdfgo.Point) *pdfgo.LinkRegion {
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region := &pdfgo.LinkRegion{Quads: quads, Rect: pdfgo.Rectangle{XMin: math.Inf(1), YMin: math.Inf(1), XMax: math.Inf(-1), YMax: math.Inf(-1)}}
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for _, quad := range quads {
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for _, p := range quad {
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region.Rect.XMin, region.Rect.YMin = min(region.Rect.XMin, p.X), min(region.Rect.YMin, p.Y)
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region.Rect.XMax, region.Rect.YMax = max(region.Rect.XMax, p.X), max(region.Rect.YMax, p.Y)
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}
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}
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return region
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}
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// flattenPDFLink 在取消和数量限制内展开动作曲线，复用标准椭圆弧转换
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// 入参: ctx 取消上下文, path 页面SVG路径
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// 返回: *canvas.Path 闭合折线路径, error 精度或复杂度错误
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func flattenPDFLink(ctx context.Context, path *canvas.Path) (*canvas.Path, error) {
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geometry := geometryFromCanvasPath(path)
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result := &canvas.Path{}
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var current, start Point
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count := 0
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var flatten func([]Point, int) error
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flatten = func(points []Point, depth int) error {
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if err := ctx.Err(); err != nil {
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return err
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}
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first, last := points[0], points[len(points)-1]
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dx, dy := last.X-first.X, last.Y-first.Y
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length := math.Hypot(dx, dy)
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distance := 0.0
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for _, point := range points[1 : len(points)-1] {
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t := 0.0
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if length > 0 {
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t = min(max((point.X-first.X)*(dx/length)+(point.Y-first.Y)*(dy/length), 0), length) / length
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}
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distance = max(distance, math.Hypot(point.X-(first.X*(1-t)+last.X*t), point.Y-(first.Y*(1-t)+last.Y*t)))
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}
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if !finite(length) || !finite(distance) {
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return fmt.Errorf("invalid PDF link curve")
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}
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if distance <= pdfLinkTolerance/2 {
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count++
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if count > pdfLinkEdgeLimit {
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return fmt.Errorf("PDF link region exceeds edge limit")
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}
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result.LineTo(last.X, -last.Y)
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return nil
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}
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if depth == 32 {
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return fmt.Errorf("PDF link curve tolerance cannot be met")
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}
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var work, left, right [4]Point
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copy(work[:], 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[:len(points)], depth+1); err != nil {
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return err
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}
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return flatten(right[:len(points)], depth+1)
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}
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for _, segment := range *geometry {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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switch segment.Verb {
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case GeometryMove:
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result.MoveTo(segment.End.X, -segment.End.Y)
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current, start = segment.End, segment.End
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case GeometryClose:
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result.Close()
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current = start
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default:
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curves := GeometryPath{segment}
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if segment.Verb == GeometryArc {
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var err error
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curves, err = arcCurves(current, segment, pdfLinkTolerance/2)
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if err != nil {
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return nil, err
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}
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if len(curves) > pdfLinkEdgeLimit-count {
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return nil, fmt.Errorf("PDF link region exceeds edge limit")
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}
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}
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for _, curve := range curves {
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var storage [4]Point
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points := append(storage[:0], current)
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if curve.Verb == GeometryQuad || curve.Verb == GeometryCubic {
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points = append(points, curve.Control1)
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}
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if curve.Verb == GeometryCubic {
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points = append(points, curve.Control2)
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}
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points = append(points, curve.End)
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if err := flatten(points, 0); err != nil {
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return nil, err
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}
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current = curve.End
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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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// x 计算非水平边在指定纵坐标处的横坐标
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// 入参: y 扫描线纵坐标
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// 返回: float64 交点横坐标
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func (e pdfLinkEdge) x(y float64) float64 {
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t := (y - e.a.Y) / (e.b.Y - e.a.Y)
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return e.a.X*(1-t) + e.b.X*t
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}
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// appendPDFLinkQuad 收集梯形，尖端退化为三角形时细分为三个非退化四边形
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// 入参: quads 已有四边形, quad 扫描带梯形
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// 返回: [][4]pdfgo.Point 四边形集合
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func appendPDFLinkQuad(quads [][4]pdfgo.Point, quad [4]pdfgo.Point) [][4]pdfgo.Point {
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epsilon := 1e-12
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for _, point := range quad {
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epsilon = max(epsilon, math.Abs(point.X)*1e-12, math.Abs(point.Y)*1e-12)
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}
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if quad[2].Y-quad[0].Y <= epsilon {
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return quads
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}
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if quad[1].X-quad[0].X <= epsilon {
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quad[0].X, quad[1].X = (quad[0].X+quad[1].X)/2, (quad[0].X+quad[1].X)/2
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}
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if quad[2].X-quad[3].X <= epsilon {
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quad[3].X, quad[2].X = (quad[3].X+quad[2].X)/2, (quad[3].X+quad[2].X)/2
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}
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var triangle [3]pdfgo.Point
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if quad[0] == quad[1] {
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if quad[2] == quad[3] {
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return quads
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}
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triangle = [3]pdfgo.Point{quad[0], quad[2], quad[3]}
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} else if quad[2] == quad[3] {
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triangle = [3]pdfgo.Point{quad[0], quad[1], quad[2]}
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} else {
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return appendValidPDFLinkQuad(quads, quad)
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}
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return appendPDFLinkTriangle(quads, triangle)
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}
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// appendPDFLinkTriangle 连接三角形重心和边中点，生成覆盖相同区域的凸四边形
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// 入参: quads 已有四边形, triangle 逆时针三角形
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// 返回: [][4]pdfgo.Point 四边形集合
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func appendPDFLinkTriangle(quads [][4]pdfgo.Point, triangle [3]pdfgo.Point) [][4]pdfgo.Point {
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center := pdfgo.Point{X: (triangle[0].X + triangle[1].X + triangle[2].X) / 3, Y: (triangle[0].Y + triangle[1].Y + triangle[2].Y) / 3}
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for i, a := range triangle {
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b, c := triangle[(i+1)%3], triangle[(i+2)%3]
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quads = appendValidPDFLinkQuad(quads, [4]pdfgo.Point{a, {X: (a.X + b.X) / 2, Y: (a.Y + b.Y) / 2}, center, {X: (a.X + c.X) / 2, Y: (a.Y + c.Y) / 2}})
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}
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return quads
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}
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// pdfLinkTurn 计算相邻边的转向，消除近共线乘积相减产生的舍入噪声
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// 入参: a 前顶点, b 当前顶点, c 后顶点
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// 返回: float64 有向面积的两倍，数值退化时为零
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func pdfLinkTurn(a, b, c pdfgo.Point) float64 {
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u, v := (b.X-a.X)*(c.Y-b.Y), (b.Y-a.Y)*(c.X-b.X)
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cross := u - v
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if math.Abs(cross) <= (math.Abs(u)+math.Abs(v))*1e-12 {
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return 0
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}
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return cross
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}
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// appendValidPDFLinkQuad 仅保留有限且非退化的逆时针凸四边形
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// 入参: quads 已有四边形, quad 候选四边形
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// 返回: [][4]pdfgo.Point 四边形集合
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func appendValidPDFLinkQuad(quads [][4]pdfgo.Point, quad [4]pdfgo.Point) [][4]pdfgo.Point {
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for i, a := range quad {
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cross := pdfLinkTurn(a, quad[(i+1)%4], quad[(i+2)%4])
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if !finite(cross) || cross <= 0 {
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return quads
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}
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}
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return append(quads, quad)
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}
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