mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
438 lines
13 KiB
Go
438 lines
13 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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"archive/zip"
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"bufio"
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"bytes"
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"fmt"
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"image"
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"image/jpeg"
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"image/png"
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"io"
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"strconv"
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"strings"
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"github.com/tdewolff/canvas"
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"github.com/tdewolff/canvas/renderers/pdf"
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"github.com/tdewolff/canvas/renderers/ps"
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"github.com/tdewolff/canvas/renderers/rasterizer"
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"github.com/tdewolff/canvas/renderers/svg"
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"golang.org/x/image/draw"
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"golang.org/x/image/math/f64"
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)
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// RenderTo 按格式渲染单页，JPEG使用95画质
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// 入参: page 页面内容, writer 输出流, format svg、pdf、eps、png、jpg、jpeg或txt
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// 返回: error 错误信息
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func (r *Renderer) RenderTo(page *PageContent, writer io.Writer, format string) error {
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_, render, err := r.outputRenderer(format)
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if err != nil {
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return err
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}
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return render(page, writer)
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}
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// outputRenderer 获取格式扩展名和渲染方法
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// 入参: format 输出格式
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// 返回: string 扩展名, func 渲染方法, error 错误信息
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func (r *Renderer) outputRenderer(format string) (string, func(*PageContent, io.Writer) error, error) {
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switch strings.ToLower(strings.TrimSpace(format)) {
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case "svg":
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return "svg", r.RenderToSVG, nil
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case "pdf":
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return "pdf", r.RenderToPDF, nil
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case "txt":
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return "txt", r.RenderToText, nil
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case "eps":
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return "eps", r.RenderToEPS, nil
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case "png":
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return "png", r.RenderToPNG, nil
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case "jpg", "jpeg":
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return "jpg", func(page *PageContent, writer io.Writer) error {
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return r.RenderToJPEG(page, writer, &jpeg.Options{Quality: 95})
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}, nil
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default:
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return "", nil, fmt.Errorf("unsupported output format %s", format)
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}
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}
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// RenderToZIP 逐页渲染并写入ZIP，文件编号按总页数补零，出错时调用方应丢弃输出
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// 入参: writer 输出流, format svg、pdf、eps、png、jpg、jpeg或txt, indices 零基页面索引，省略则全部，按原页序去重
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// 返回: error 错误信息
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func (r *Renderer) RenderToZIP(writer io.Writer, format string, indices ...int) error {
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extension, render, err := r.outputRenderer(format)
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if err != nil {
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return err
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}
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count, err := r.Reader.PageCount()
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if err != nil {
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return err
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}
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indices, err = exportPageIndices(count, indices)
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if err != nil {
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return err
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}
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archive := zip.NewWriter(writer)
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method := zip.Deflate
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if extension == "png" || extension == "jpg" {
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method = zip.Store
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}
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width := len(strconv.Itoa(count))
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if err := r.exportProgress(0, len(indices)); err != nil {
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return err
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}
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for i, index := range indices {
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page, err := r.Reader.PageContentByIndex(index)
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if err != nil {
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return fmt.Errorf("failed to read page %d: %w", index+1, err)
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}
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entry, err := archive.CreateHeader(&zip.FileHeader{
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Name: fmt.Sprintf("%0*d.%s", width, index+1, extension),
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Method: method,
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})
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if err != nil {
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return err
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}
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if err := render(page, entry); err != nil {
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return fmt.Errorf("failed to export page %d: %w", index+1, err)
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}
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if err := r.exportProgress(i+1, len(indices)); err != nil {
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return err
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}
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}
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return archive.Close()
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}
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// RenderToText 导出页面原文为UTF-8文本，以换行分隔非空文本对象
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// 入参: page 页面内容, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderToText(page *PageContent, writer io.Writer) error {
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text, err := r.PageText(page)
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if err != nil {
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return err
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}
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_, err = io.WriteString(writer, text.String())
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return err
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}
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// RenderToMultiPageText 逐页导出UTF-8原文，以换行分隔非空页面，出错时调用方应丢弃输出
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// 入参: writer 输出流, indices 零基页面索引，省略则全部，按原页序去重
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// 返回: error 错误信息
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func (r *Renderer) RenderToMultiPageText(writer io.Writer, indices ...int) error {
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count, err := r.Reader.PageCount()
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if err != nil {
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return err
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}
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indices, err = exportPageIndices(count, indices)
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if err != nil {
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return err
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}
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if err := r.exportProgress(0, len(indices)); err != nil {
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return err
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}
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written := false
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for i, index := range indices {
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text, err := r.PageTextByIndex(index)
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if err != nil {
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return fmt.Errorf("failed to extract page %d text: %w", index+1, err)
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}
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if value := text.String(); value != "" {
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if written {
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if _, err := io.WriteString(writer, "\n"); err != nil {
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return err
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}
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}
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if _, err := io.WriteString(writer, value); err != nil {
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return err
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}
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written = true
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}
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if err := r.exportProgress(i+1, len(indices)); 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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// exportProgress 回报导出进度并传递调用方的停止原因
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// 入参: completed 已处理页数, total 总页数
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// 返回: error 停止原因
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func (r *Renderer) exportProgress(completed, total int) error {
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if r.OnExportProgress != nil {
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return r.OnExportProgress(completed, total)
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}
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return nil
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}
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// rasterRenderer 保留页面物理尺寸的光栅渲染器
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type rasterRenderer struct {
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*rasterizer.Rasterizer
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width, height float64
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dpmm float64
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linear bool
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}
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// Size 返回页面物理尺寸
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// 返回: float64 宽度, float64 高度
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func (r *rasterRenderer) Size() (float64, float64) {
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return r.width, r.height
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}
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// RenderImage 使用底层图片完成平移和缩放
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// 入参: img 图片对象, m 图片变换矩阵
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func (r *rasterRenderer) RenderImage(img image.Image, m canvas.Matrix) {
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if !r.linear || m[0][1] != 0 || m[1][0] != 0 {
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r.Rasterizer.RenderImage(img, m)
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return
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}
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origin := m.Dot(canvas.Point{Y: float64(img.Bounds().Dy())}).Mul(r.dpmm)
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m = m.Scale(r.dpmm, r.dpmm)
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transform := f64.Aff3{m[0][0], -m[0][1], origin.X, -m[1][0], m[1][1], float64(r.Bounds().Dy()) - origin.Y}
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draw.CatmullRom.Transform(r.Image, transform, img, img.Bounds(), draw.Over, nil)
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}
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// RenderToImage 渲染为光栅图
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// 入参: page 页面内容
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// 返回: image.Image 图像对象, error 错误信息
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func (r *Renderer) RenderToImage(page *PageContent) (image.Image, error) {
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box, err := r.GetPageBox(page)
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if err != nil {
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return nil, err
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}
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dpmm := r.DPI / 25.4
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colorSpace := canvas.DefaultColorSpace
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_, linear := colorSpace.(canvas.LinearColorSpace)
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raster := &rasterRenderer{
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Rasterizer: rasterizer.New(box.W, box.H, canvas.DPMM(dpmm), colorSpace),
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width: box.W,
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height: box.H,
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dpmm: dpmm,
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linear: linear,
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}
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if err := r.RenderPageToContext(canvas.NewContext(raster), page); err != nil {
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return nil, err
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}
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raster.Close()
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return raster.Image, nil
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}
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// RenderToPNG 渲染为PNG，像素尺寸由DPI决定
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// 入参: page 页面内容, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderToPNG(page *PageContent, writer io.Writer) error {
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img, err := r.RenderToImage(page)
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if err != nil {
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return err
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}
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return png.Encode(writer, img)
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}
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// RenderToJPEG 渲染为白底JPEG，像素尺寸由DPI决定
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// 入参: page 页面内容, writer 输出流, options 编码选项，nil使用标准库默认值
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// 返回: error 错误信息
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func (r *Renderer) RenderToJPEG(page *PageContent, writer io.Writer, options *jpeg.Options) error {
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img, err := r.RenderToImage(page)
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if err != nil {
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return err
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}
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return jpeg.Encode(writer, fillWhiteBackground(img), options)
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}
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// fillWhiteBackground 填充白色背景，复用当前导出图片的RGBA像素
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// 入参: img 图片对象
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// 返回: image.Image 图片对象
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func fillWhiteBackground(img image.Image) image.Image {
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bounds := img.Bounds()
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if rgba, ok := img.(*image.RGBA); ok {
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for y := 0; y < bounds.Dy(); y++ {
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row := rgba.Pix[y*rgba.Stride : y*rgba.Stride+bounds.Dx()*4]
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for i := 0; i < len(row); i += 4 {
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if alpha := 255 - row[i+3]; alpha != 0 {
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row[i] += alpha
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row[i+1] += alpha
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row[i+2] += alpha
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row[i+3] = 255
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}
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}
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}
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return rgba
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}
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dst := image.NewRGBA(bounds)
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draw.Draw(dst, bounds, image.White, image.Point{}, draw.Src)
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draw.Draw(dst, bounds, img, bounds.Min, draw.Over)
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return dst
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}
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// RenderToSVG 渲染为SVG
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// 入参: page 页面内容, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderToSVG(page *PageContent, writer io.Writer) error {
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c, err := r.renderPage(page)
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if err != nil {
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return err
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}
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buffer := bufio.NewWriter(writer)
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renderer := svg.New(buffer, c.W, c.H, nil)
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c.RenderTo(renderer)
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if err := renderer.Close(); err != nil {
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return err
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}
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return buffer.Flush()
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}
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// replacePDFProducer 替换PDF的Producer属性
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// 入参: data PDF字节数据
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// 返回: []byte 替换后的PDF字节数据
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func replacePDFProducer(data []byte) []byte {
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old := []byte("/Producer(tdewolff/canvas)")
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idx := bytes.LastIndex(data, old)
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if idx < 0 {
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return data
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}
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dst := []byte("/Producer(xiaoqidun/ofdgo)")
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copy(data[idx:idx+len(old)], dst)
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return data
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}
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// RenderToPDF 渲染为PDF
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// 入参: page 页面内容, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderToPDF(page *PageContent, writer io.Writer) error {
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box, err := r.GetPageBox(page)
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if err != nil {
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return err
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}
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pages := []pdfPage{{Content: page, Box: box}}
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return r.renderPDFPages(pages, writer, nil)
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}
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// RenderToEPS 渲染为EPS
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// 入参: page 页面内容, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderToEPS(page *PageContent, writer io.Writer) error {
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c, err := r.renderPage(page)
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if err != nil {
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return err
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}
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options := ps.DefaultOptions
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options.Format = ps.EncapsulatedPostScript
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buffer := bufio.NewWriter(writer)
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renderer := ps.New(buffer, c.W, c.H, &options)
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c.RenderTo(renderer)
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if err := renderer.Close(); err != nil {
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return err
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}
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return buffer.Flush()
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}
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// RenderToMultiPagePDF 将文档页面导出为多页PDF
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// 入参: writer 输出流, indices 零基页面索引，省略则全部，按原页序去重
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// 返回: error 错误信息
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func (r *Renderer) RenderToMultiPagePDF(writer io.Writer, indices ...int) error {
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doc, err := r.Reader.Doc()
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if err != nil {
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return err
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}
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indices, err = exportPageIndices(len(doc.Pages.Page), indices)
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if err != nil {
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return err
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}
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if err := r.exportProgress(0, len(indices)); err != nil {
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return err
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}
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pages := make([]pdfPage, len(indices))
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for i, index := range indices {
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page, err := r.Reader.PageContent(doc.Pages.Page[index])
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if err != nil {
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return fmt.Errorf("failed to read page %d: %w", index+1, err)
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}
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box, err := r.GetPageBox(page)
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if err != nil {
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return fmt.Errorf("failed to read page %d area: %w", index+1, err)
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}
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pages[i] = pdfPage{Content: page, Box: box}
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}
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return r.renderPDFPages(pages, writer, r.OnExportProgress)
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}
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// RenderPagesToPDF 按指定顺序导出已解析的页面，复用调用方的页面缓存
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// 入参: contents 页面内容列表, writer 输出流
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// 返回: error 错误信息
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func (r *Renderer) RenderPagesToPDF(contents []*PageContent, writer io.Writer) error {
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if len(contents) == 0 {
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return fmt.Errorf("no pages found")
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}
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if err := r.exportProgress(0, len(contents)); err != nil {
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return err
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}
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pages := make([]pdfPage, len(contents))
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for i, page := range contents {
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box, err := r.GetPageBox(page)
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if err != nil {
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return fmt.Errorf("failed to read page %d area: %w", i+1, err)
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}
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pages[i] = pdfPage{Content: page, Box: box}
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}
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return r.renderPDFPages(pages, writer, r.OnExportProgress)
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}
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// renderPDFPages 渲染页面并复用调用方的字节缓冲
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// 入参: pages 页面列表, writer 输出流, progress 页面处理进度
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// 返回: error 错误信息
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func (r *Renderer) renderPDFPages(pages []pdfPage, writer io.Writer, progress func(int, int) error) error {
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navigation := newPDFNavigation(r, r.Reader.doc, pages)
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buf, direct := writer.(*bytes.Buffer)
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if !direct {
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buf = &bytes.Buffer{}
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}
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start := buf.Len()
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p := pdf.New(buf, pages[0].Box.W, pages[0].Box.H, nil)
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renderer := &pdfRenderer{PDF: p, glyphPaths: make(map[*canvas.Path]*canvas.Path)}
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var info DocInfo
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if docInfo, err := r.Reader.DocInfo(); err == nil {
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info = *docInfo
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}
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p.SetInfo(info.Title, info.Subject, "", info.Author, "xiaoqidun/ofdgo")
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for i, page := range pages {
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if i > 0 {
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p.NewPage(page.Box.W, page.Box.H)
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}
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navigation.apply(p, i)
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if err := r.renderPageToContext(canvas.NewContext(renderer), page.Content, true); err != nil {
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buf.Truncate(start)
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return fmt.Errorf("failed to render page %d: %w", i+1, err)
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}
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pages[i].Content = nil
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if progress != nil {
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if err := progress(i+1, len(pages)); err != nil {
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buf.Truncate(start)
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return err
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}
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}
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}
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if err := p.Close(); err != nil {
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buf.Truncate(start)
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return err
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}
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data := replacePDFProducer(buf.Bytes()[start:])
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if direct {
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return nil
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}
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_, err := writer.Write(data)
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return err
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}
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