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// 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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"reflect"
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"github.com/xiaoqidun/pdfgo"
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)
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// group 将不透明图元的透明组转换为互不重叠的填充区域，保留矢量与组不透明度
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// 入参: mark 组边界状态, walk 组内容访问函数, visitor 页面访问器
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// 返回: error 不支持的组内容或转换错误
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func (p *pdfImporter) group(mark pdfgo.GroupMark, walk func(pdfgo.Visitor) error, visitor pdfgo.Visitor) error {
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if err := p.flushPath(); err != nil {
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return err
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}
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if mark.SoftMask != nil {
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clip, err := p.maskClip(mark.SoftMask)
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if err != nil {
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return err
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}
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original := walk
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walk = func(v pdfgo.Visitor) error {
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return original(pdfClippedVisitor(v, clip))
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}
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}
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if mark.Alpha == 1 {
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if err := walk(visitor); err != nil {
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return err
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}
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return p.flushPath()
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}
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geometry, err := p.editor.Geometry()
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if err != nil {
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return err
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}
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type paintRegion struct {
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paint pdfgo.Paint
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path GeometryPath
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}
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var regions []paintRegion
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var combined GeometryPath
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var paint *pdfgo.Paint
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var clips []pdfgo.Path
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scale := math.Hypot(p.matrix[0], p.matrix[1])
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collect := pdfgo.Visitor{Warning: visitor.Warning}
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collect.Path = func(path pdfgo.PathMark) error {
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shape, err := ParseGeometryPath(p.pathData(path.Path, Box{}))
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if err != nil {
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return err
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}
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for _, stroke := range []bool{false, true} {
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if stroke && !path.Stroke || !stroke && !path.Fill {
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continue
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}
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color, overprint := path.Style.Fill, path.Style.FillOverprint
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if stroke {
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color, overprint = path.Style.Stroke, path.Style.StrokeOverprint
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}
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if color.Alpha != 1 || color.Axial != nil || overprint && !pdfOpaqueBlack(color) {
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return &pdfgo.UnsupportedError{Feature: "transparent or overprinted group content"}
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}
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if paint == nil {
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paint, clips = &color, path.Style.Clips
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} else if !reflect.DeepEqual(clips, path.Style.Clips) {
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return &pdfgo.UnsupportedError{Feature: "independently clipped transparent group"}
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} else if !reflect.DeepEqual(*paint, color) {
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regions = append(regions, paintRegion{*paint, combined})
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combined = nil
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paint = &color
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}
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outline := shape
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evenOdd := path.Path.EvenOdd
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if stroke {
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dashes := make([]float64, len(path.Style.Dash))
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for i, dash := range path.Style.Dash {
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dashes[i] = dash * scale
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}
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outline, err = geometry.Stroke(shape, StrokeOptions{Width: path.Style.LineWidth * scale, Cap: []string{"Butt", "Round", "Square"}[path.Style.Cap], Join: []string{"Miter", "Round", "Bevel"}[path.Style.Join], MiterLimit: path.Style.MiterLimit, DashOffset: path.Style.DashPhase * scale, Dashes: dashes, Tolerance: 0.001})
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if err != nil {
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return err
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}
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evenOdd = false
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}
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outline, err = geometry.Normalize(outline, evenOdd)
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if err != nil {
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return err
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}
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combined = append(combined, outline...)
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}
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return nil
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}
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if err := walk(collect); err != nil {
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return err
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}
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if len(combined) == 0 {
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return nil
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}
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regions = append(regions, paintRegion{*paint, combined})
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var covered GeometryPath
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for i := len(regions) - 1; i >= 0; i-- {
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region := regions[i]
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visible := region.path
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if len(covered) > 0 {
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visible, err = geometry.Combine(visible, covered, GeometrySubtract)
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if err != nil {
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return err
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}
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}
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if i > 0 {
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covered, err = geometry.Combine(covered, region.path, GeometryUnion)
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if err != nil {
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return err
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}
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}
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if len(visible) == 0 {
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continue
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}
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box, err := geometry.Bounds(visible)
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if err != nil {
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return err
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}
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if box.W == 0 || box.H == 0 {
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continue
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}
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visible, err = geometry.Transform(visible, TranslationMatrix(-box.X, -box.Y))
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if err != nil {
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return err
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}
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data, err := visible.OFD()
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if err != nil {
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return err
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}
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region.paint.Alpha = mark.Alpha
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fill, stroke := true, false
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object := PathObject{Boundary: pdfBoundary(box), AbbreviatedData: data, Fill: &fill, Stroke: &stroke, FillColor: p.color(region.paint), Clips: p.clips(clips, box)}
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p.objects = append(p.objects, GraphicObject{Type: "PathObject", PathObject: object})
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p.report.PathObjects++
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}
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return nil
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}
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// pdfClippedVisitor 为图元及嵌套组附加裁剪，保留未提供的访问能力
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// 入参: visitor 图元访问器, clip 页面坐标裁剪
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// 返回: pdfgo.Visitor 裁剪访问器
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func pdfClippedVisitor(visitor pdfgo.Visitor, clip pdfgo.Path) pdfgo.Visitor {
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result := visitor
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if visitor.Path != nil {
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result.Path = func(mark pdfgo.PathMark) error {
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mark.Style.Clips = append(append([]pdfgo.Path(nil), mark.Style.Clips...), clip)
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return visitor.Path(mark)
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}
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}
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if visitor.Text != nil {
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result.Text = func(mark pdfgo.TextMark) error {
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mark.Style.Clips = append(append([]pdfgo.Path(nil), mark.Style.Clips...), clip)
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return visitor.Text(mark)
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}
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}
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if visitor.Image != nil {
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result.Image = func(mark pdfgo.ImageMark) error {
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mark.Style.Clips = append(append([]pdfgo.Path(nil), mark.Style.Clips...), clip)
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return visitor.Image(mark)
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}
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}
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if visitor.Group != nil {
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result.Group = func(mark pdfgo.GroupMark, walk func(pdfgo.Visitor) error) error {
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return visitor.Group(mark, func(v pdfgo.Visitor) error { return walk(pdfClippedVisitor(v, clip)) })
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}
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}
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return result
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}
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// maskClip 将二值亮度蒙版转换为标准矢量裁剪，不栅格化原图元
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// 入参: mask PDF蒙版
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// 返回: pdfgo.Path 页面坐标裁剪路径, error 不可精确转换或几何错误
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func (p *pdfImporter) maskClip(mask *pdfgo.SoftMask) (pdfgo.Path, error) {
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if clip, ok := p.maskClips[mask]; ok {
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return clip, nil
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}
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geometry, err := p.editor.Geometry()
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if err != nil {
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return pdfgo.Path{}, err
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}
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opacity := func(v float64) (bool, error) {
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v = math.Max(0, math.Min(1, mask.Transfer[0]+v*(mask.Transfer[1]-mask.Transfer[0])))
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if v != 0 && v != 1 {
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return false, &pdfgo.UnsupportedError{Feature: "nonbinary luminosity mask"}
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}
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return v == 1, nil
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}
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background, err := opacity(mask.Background)
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if err != nil {
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return pdfgo.Path{}, err
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}
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box := p.pageBox
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var region GeometryPath
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if background {
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region, err = ParseGeometryPath(pdfNumbersPathBox(box))
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if err != nil {
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return pdfgo.Path{}, err
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}
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region, err = geometry.Normalize(region, false)
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if err != nil {
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return pdfgo.Path{}, err
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}
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}
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identity := pdfImporter{matrix: pdfgo.Identity()}
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var visitor pdfgo.Visitor
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visitor.Group = func(mark pdfgo.GroupMark, walk func(pdfgo.Visitor) error) error {
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if mark.Alpha != 1 || mark.SoftMask != nil {
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return &pdfgo.UnsupportedError{Feature: "transparent mask group"}
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}
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return walk(visitor)
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}
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visitor.Path = func(mark pdfgo.PathMark) error {
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paint := mark.Style.Fill
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if !mark.Fill || mark.Stroke || paint.Alpha != 1 || paint.CMYK != nil || paint.Axial != nil || paint.RGB[0] != paint.RGB[1] || paint.RGB[1] != paint.RGB[2] || mark.Style.SoftMask != nil {
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return &pdfgo.UnsupportedError{Feature: "nonbinary mask graphic"}
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}
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visible, err := opacity(paint.RGB[0])
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if err != nil {
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return err
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}
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shape, err := ParseGeometryPath(identity.pathData(mark.Path, Box{}))
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if err != nil {
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return err
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}
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shape, err = geometry.Normalize(shape, mark.Path.EvenOdd)
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if err != nil {
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return err
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}
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for _, clip := range mark.Style.Clips {
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c, err := ParseGeometryPath(identity.pathData(clip, Box{}))
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if err != nil {
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return err
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}
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c, err = geometry.Normalize(c, clip.EvenOdd)
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if err != nil {
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return err
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}
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shape, err = geometry.Combine(shape, c, GeometryIntersect)
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if err != nil {
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return err
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}
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}
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operation := GeometrySubtract
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if visible {
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operation = GeometryUnion
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}
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region, err = geometry.Combine(region, shape, operation)
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return err
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}
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if err := mask.Walk(visitor); err != nil {
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return pdfgo.Path{}, err
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}
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path := pdfgo.Path{}
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for _, segment := range region {
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point := func(p Point) pdfgo.Point { return pdfgo.Point{X: p.X, Y: p.Y} }
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switch segment.Verb {
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case GeometryMove:
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path.Segments = append(path.Segments, pdfgo.Segment{Operator: "M", Points: []pdfgo.Point{point(segment.End)}})
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case GeometryLine:
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path.Segments = append(path.Segments, pdfgo.Segment{Operator: "L", Points: []pdfgo.Point{point(segment.End)}})
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case GeometryCubic:
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path.Segments = append(path.Segments, pdfgo.Segment{Operator: "B", Points: []pdfgo.Point{point(segment.Control1), point(segment.Control2), point(segment.End)}})
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case GeometryClose:
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path.Segments = append(path.Segments, pdfgo.Segment{Operator: "C"})
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default:
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return pdfgo.Path{}, fmt.Errorf("unsupported mask geometry verb %d", segment.Verb)
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}
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}
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if p.maskClips == nil {
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p.maskClips = make(map[*pdfgo.SoftMask]pdfgo.Path)
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}
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p.maskClips[mask] = path
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return path, nil
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}
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// pdfNumbersPathBox 编码PDF坐标矩形的闭合路径
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// 入参: box 矩形边界
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// 返回: string 紧缩路径
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func pdfNumbersPathBox(box pdfgo.Rectangle) string {
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return "M " + pdfNumbers(box.XMin, box.YMin) + " L " + pdfNumbers(box.XMax, box.YMin) + " L " + pdfNumbers(box.XMax, box.YMax) + " L " + pdfNumbers(box.XMin, box.YMax) + " C"
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}
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// maskStyle 将独立图元的二值蒙版附加到裁剪链
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// 入参: style 图形状态
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// 返回: pdfgo.Style 转换后的状态, error 蒙版转换错误
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func (p *pdfImporter) maskStyle(style pdfgo.Style) (pdfgo.Style, error) {
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if style.SoftMask == nil {
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return style, nil
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}
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clip, err := p.maskClip(style.SoftMask)
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if err != nil {
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return style, err
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}
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style.Clips = append(append([]pdfgo.Path(nil), style.Clips...), clip)
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style.SoftMask = nil
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return style, nil
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}
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