mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 17:27:08 +08:00
331 lines
11 KiB
Go
331 lines
11 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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"math"
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"reflect"
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"strings"
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"unicode/utf8"
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"github.com/xiaoqidun/pdfgo"
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)
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// pdfTextReplacement 记录一个完整替换区段的文字数量与转换状态
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type pdfTextReplacement struct {
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text *pdfgo.ReplacementText
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count int
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matched int
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offset int64
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blocked bool
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applied bool
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identity bool
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}
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// pdfTextReplacements 按绘制顺序收集替换区段，避免拆分或重复写入原文
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type pdfTextReplacements struct {
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importer *pdfImporter
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spans map[*pdfgo.ReplacementText]*pdfTextReplacement
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order []*pdfTextReplacement
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widget bool
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}
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// span 查找最外层替换区段，相邻区段即使原文相同也分别保留
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// 入参: text 替换文本
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// 返回: *pdfTextReplacement 区段状态，未声明时为空
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func (r *pdfTextReplacements) span(text *pdfgo.ReplacementText) *pdfTextReplacement {
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if text == nil {
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return nil
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}
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if r.spans == nil {
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r.spans = make(map[*pdfgo.ReplacementText]*pdfTextReplacement)
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}
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first := text
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for text.Parent != nil && r.spans[text] == nil {
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text = text.Parent
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}
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span := r.spans[text]
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if span == nil {
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span = &pdfTextReplacement{text: text}
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r.spans[text] = span
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r.order = append(r.order, span)
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}
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for first != text {
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r.spans[first] = span
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first = first.Parent
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}
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return span
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}
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// block 标记无法仅用字符与字形变换表达的区段
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// 入参: text 替换文本
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func (r *pdfTextReplacements) block(text *pdfgo.ReplacementText) {
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if span := r.span(text); span != nil {
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span.blocked = true
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}
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}
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// markedContent 核对已接入的替换文本属性，不静默丢弃其他内容语义
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// 入参: mark 内容标记
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// 返回: error 未支持的语义错误
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func (r *pdfTextReplacements) markedContent(mark pdfgo.MarkedContentMark) error {
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if mark.Operator == "EMC" {
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return nil
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}
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if mark.Tag == "OC" {
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kind, err := r.importer.reader.Resolve(mark.Properties["Type"])
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if err != nil {
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return err
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}
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if kind == pdfgo.Name("OCG") || kind == pdfgo.Name("OCMD") {
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return nil
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}
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}
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if r.widget && mark.Tag == "Tx" && len(mark.Properties) == 0 {
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return nil
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}
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if mark.Replacement != nil && len(mark.Properties) == 1 {
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return nil
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}
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if r.importer.warning == nil {
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return &pdfgo.UnsupportedError{Feature: "marked content requiring semantic preservation"}
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}
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r.importer.warning(pdfgo.Diagnostic{Offset: mark.Offset, Message: "marked content " + string(mark.Tag) + " not preserved"})
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return nil
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}
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// apply 合并可等价表示的替换区段，原文相同但样式不同的区段保留原图元
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// 入参: nodes 原始图元
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// 返回: []pdfCompositeNode 转换图元, error 取消或语义转换错误
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func (r *pdfTextReplacements) apply(nodes []pdfCompositeNode) ([]pdfCompositeNode, error) {
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if len(r.order) == 0 {
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return nodes, nil
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}
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if err := r.count(nodes, false); err != nil {
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return nil, err
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}
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for _, span := range r.order {
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span.identity = !span.blocked && span.count > 0 && span.matched == len(span.text.Text)
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}
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var err error
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nodes, err = r.merge(nodes)
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if err != nil {
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return nil, err
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}
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for _, span := range r.order {
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if span.applied || span.identity || !span.blocked && span.count == 0 && span.text.Text == "" {
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continue
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}
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if r.importer.warning == nil {
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return nil, &pdfgo.UnsupportedError{Feature: "ActualText span without equivalent OFD glyph mapping"}
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}
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r.importer.warning(pdfgo.Diagnostic{Offset: span.offset, Message: "PDF ActualText span not preserved; original appearance retained"})
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}
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r.clear(nodes)
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return nodes, nil
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}
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// count 统计区段文字并逐字核对原文，排除需要组级合成的内容
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// 入参: nodes 图元, blocked 上层组是否阻止直接转换
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// 返回: error 取消错误
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func (r *pdfTextReplacements) count(nodes []pdfCompositeNode, blocked bool) error {
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for _, node := range nodes {
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if err := r.importer.ctx.Err(); err != nil {
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return err
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}
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if node.text != nil {
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if span := r.span(node.text.Replacement); span != nil {
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span.count++
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span.blocked = span.blocked || blocked
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for i, glyph := range node.text.Glyphs {
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if span.matched < 0 {
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break
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}
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if i%256 == 0 {
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if err := r.importer.ctx.Err(); err != nil {
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return err
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}
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}
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if glyph.Text == "" || !strings.HasPrefix(span.text.Text[span.matched:], glyph.Text) {
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span.matched = -1
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break
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}
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span.matched += len(glyph.Text)
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}
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}
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}
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childBlocked := blocked
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if group := node.group; group != nil && node.textObject == nil {
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opaque, err := node.opaque(group.ColorSpace)
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childBlocked = childBlocked || !opaque || err != nil || group.ColorSpace != nil && !group.ColorSpace.SRGBEquivalent()
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}
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if err := r.count(node.children, childBlocked); err != nil {
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return err
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}
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}
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return nil
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}
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// merge 合并同层连续图元，保留原始绘制顺序与字形坐标
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// 入参: nodes 图元
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// 返回: []pdfCompositeNode 合并结果, error 取消错误
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func (r *pdfTextReplacements) merge(nodes []pdfCompositeNode) ([]pdfCompositeNode, error) {
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result := nodes[:0]
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for i := 0; i < len(nodes); {
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if err := r.importer.ctx.Err(); err != nil {
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return nil, err
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}
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node := nodes[i]
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var err error
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node.children, err = r.merge(node.children)
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if err != nil {
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return nil, err
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}
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end := i + 1
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combined := false
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first := node.text
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if first == nil && node.textObject != nil && len(node.children) != 0 {
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first = node.children[0].text
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}
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if first != nil {
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if span := r.span(first.Replacement); span != nil && !span.applied && !span.blocked && span.text.Text != "" && !(span.identity && span.count == 1) {
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var marks []pdfCompositeNode
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for end = i; end < len(nodes); end++ {
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current := nodes[end]
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children := current.children
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if current.text != nil {
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children = nodes[end : end+1]
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} else if current.textObject == nil {
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break
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}
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valid := len(children) != 0
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for _, child := range children {
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if child.text == nil || r.span(child.text.Replacement) != span {
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valid = false
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break
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}
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}
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if !valid {
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break
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}
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marks = append(marks, children...)
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}
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end = max(end, i+1)
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if len(marks) == span.count {
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if mark, ok := pdfMergeReplacement(marks, span.text); ok {
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if node.text != nil {
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node.text = mark
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} else {
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node.children = []pdfCompositeNode{{text: mark}}
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}
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span.applied = true
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combined = true
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}
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}
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}
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}
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node.formCount = 0
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result = append(result, node)
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if !combined {
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for _, remaining := range nodes[i+1 : end] {
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remaining.formCount = 0
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result = append(result, remaining)
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}
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}
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i = end
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}
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clear(nodes[len(result):])
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return result, nil
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}
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// clear 清除无需替换及未转换的区段引用，防止局部绘制重复使用整段原文
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// 入参: nodes 图元
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func (r *pdfTextReplacements) clear(nodes []pdfCompositeNode) {
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for _, node := range nodes {
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if node.text != nil {
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if span := r.span(node.text.Replacement); span != nil && !span.applied {
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node.text.Replacement = nil
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}
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}
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r.clear(node.children)
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}
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}
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// pdfMergeReplacement 统一同一替换区段内的坐标原点，不重新塑形或调整字距
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// 入参: nodes 连续文字图元, replacement 整段原文
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// 返回: *pdfgo.TextMark 合并文字, bool 是否可等价合并
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func pdfMergeReplacement(nodes []pdfCompositeNode, replacement *pdfgo.ReplacementText) (*pdfgo.TextMark, bool) {
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first := nodes[0].text
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style := first.Style
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paint := style.Fill
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if first.Font == nil || len(first.Font.Program) == 0 || first.Mode != 0 || first.Size <= 0 || first.HorizontalScale <= 0 || first.Clip != nil || style.SoftMask != nil || style.Transfer != nil || style.AlphaIsShape || style.FillOverprint || paint.Alpha != 1 || !pdfNormalBlend(style.BlendMode) || paint.Tiling != nil || paint.Axial != nil || paint.Radial != nil || paint.Mesh != nil || paint.Function != nil {
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return nil, false
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}
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inverse, ok := first.Matrix.Inverse()
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if !ok {
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return nil, false
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}
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count := 0
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for _, node := range nodes {
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mark := node.text
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if mark.Font != first.Font || mark.Size != first.Size || mark.HorizontalScale != first.HorizontalScale || mark.Mode != first.Mode || mark.Clip != nil || len(mark.Glyphs) != len(mark.Positions) || !reflect.DeepEqual(mark.Style, style) {
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return nil, false
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}
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if mark.Matrix[0] != first.Matrix[0] || mark.Matrix[1] != first.Matrix[1] || mark.Matrix[2] != first.Matrix[2] || mark.Matrix[3] != first.Matrix[3] {
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return nil, false
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}
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count += len(mark.Glyphs)
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}
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if count == 0 {
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return nil, false
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}
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merged := *first
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merged.Replacement = replacement
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merged.Glyphs = make([]pdfgo.Glyph, 0, count)
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merged.Positions = make([]pdfgo.Point, 0, count)
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for _, node := range nodes {
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mark := node.text
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dx, dy := mark.Matrix[4]-first.Matrix[4], mark.Matrix[5]-first.Matrix[5]
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offset := pdfgo.Point{X: inverse[0]*dx + inverse[2]*dy, Y: inverse[1]*dx + inverse[3]*dy}
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for _, point := range mark.Positions {
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point.X += offset.X
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point.Y += offset.Y
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if math.IsNaN(point.X) || math.IsNaN(point.Y) || math.IsInf(point.X, 0) || math.IsInf(point.Y, 0) {
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return nil, false
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}
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merged.Positions = append(merged.Positions, point)
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}
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merged.Glyphs = append(merged.Glyphs, mark.Glyphs...)
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}
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return &merged, true
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}
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// pdfApplyReplacement 将整段原文映射到全部字形，字形位移遵循GB/T 33190的文字定位规则
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// 入参: object 文字对象, text 整段原文, positions 原始字形位置
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func pdfApplyReplacement(object *TextObject, text string, positions []pdfgo.Point) {
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const unit = 25.4 / 72
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glyphs := make([]string, len(object.CGTransform))
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for i, transform := range object.CGTransform {
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glyphs[i] = transform.Glyphs
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}
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dx, dy := make([]float64, len(positions)-1), make([]float64, len(positions)-1)
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for i := 1; i < len(positions); i++ {
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dx[i-1] = (positions[i].X - positions[i-1].X) * unit
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dy[i-1] = -(positions[i].Y - positions[i-1].Y) * unit
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}
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object.TextCode = []TextCode{{X: pdfNumbers(positions[0].X * unit), Y: pdfNumbers(-positions[0].Y * unit), DeltaX: pdfNumbers(dx...), DeltaY: pdfNumbers(dy...), Value: escapeOFDText(text)}}
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object.CGTransform = []CGTransform{{CodeCount: utf8.RuneCountInString(text), GlyphCount: len(glyphs), Glyphs: strings.Join(glyphs, " ")}}
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}
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