refactor(重构代码): 拆分代码，提升代码质量

ofdgo_renderer_output.go

@@ -0,0 +1,134 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"io"
+
+	"github.com/tdewolff/canvas"
+	"github.com/tdewolff/canvas/renderers"
+	"github.com/tdewolff/canvas/renderers/pdf"
+	"github.com/tdewolff/canvas/renderers/rasterizer"
+)
+
+// RenderToImage 渲染为光栅图
+// 入参: page 页面内容
+// 返回: image.Image 图像对象, error 错误信息
+func (r *Renderer) RenderToImage(page *PageContent) (image.Image, error) {
+	c, err := r.RenderPage(page)
+	if err != nil {
+		return nil, err
+	}
+	dpmm := r.DPI / 25.4
+	return rasterizer.Draw(c, canvas.DPMM(dpmm), canvas.DefaultColorSpace), nil
+}
+
+// RenderToSVG 渲染为SVG
+// 入参: page 页面内容, writer 输出流
+// 返回: error 错误信息
+func (r *Renderer) RenderToSVG(page *PageContent, writer io.Writer) error {
+	c, err := r.RenderPage(page)
+	if err != nil {
+		return err
+	}
+	return c.Write(writer, renderers.SVG())
+}
+
+// replacePDFProducer 替换PDF的Producer属性
+// 入参: data PDF字节数据
+// 返回: []byte 替换后的PDF字节数据
+func replacePDFProducer(data []byte) []byte {
+	old := []byte("/Producer(tdewolff/canvas)")
+	idx := bytes.LastIndex(data, old)
+	if idx < 0 {
+		return data
+	}
+	dst := []byte("/Producer(xiaoqidun/ofdgo)")
+	result := make([]byte, 0, len(data)-len(old)+len(dst))
+	return append(append(append(result, data[:idx]...), dst...), data[idx+len(old):]...)
+}
+
+// RenderToPDF 渲染为PDF
+// 入参: page 页面内容, writer 输出流
+// 返回: error 错误信息
+func (r *Renderer) RenderToPDF(page *PageContent, writer io.Writer) error {
+	c, err := r.RenderPage(page)
+	if err != nil {
+		return err
+	}
+	var buf bytes.Buffer
+	p := pdf.New(&buf, c.W, c.H, nil)
+	p.SetInfo("", "", "", "", "xiaoqidun/ofdgo")
+	c.RenderTo(p)
+	if err := p.Close(); err != nil {
+		return err
+	}
+	_, err = writer.Write(replacePDFProducer(buf.Bytes()))
+	return err
+}
+
+// RenderToEPS 渲染为EPS
+// 入参: page 页面内容, writer 输出流
+// 返回: error 错误信息
+func (r *Renderer) RenderToEPS(page *PageContent, writer io.Writer) error {
+	c, err := r.RenderPage(page)
+	if err != nil {
+		return err
+	}
+	return c.Write(writer, renderers.EPS())
+}
+
+// RenderToMultiPagePDF 将整个文档导出为多页PDF
+// 入参: writer 输出流
+// 返回: error 错误信息
+func (r *Renderer) RenderToMultiPagePDF(writer io.Writer) error {
+	doc, err := r.Reader.Doc()
+	if err != nil {
+		return err
+	}
+	if len(doc.Pages.Page) == 0 {
+		return fmt.Errorf("no pages found")
+	}
+	var buf bytes.Buffer
+	var p *pdf.PDF
+	for _, pgRef := range doc.Pages.Page {
+		page, err := r.Reader.PageContent(pgRef)
+		if err != nil {
+			continue
+		}
+		c, err := r.RenderPage(page)
+		if err != nil {
+			continue
+		}
+		if p == nil {
+			p = pdf.New(&buf, c.W, c.H, nil)
+			p.SetInfo("", "", "", "", "xiaoqidun/ofdgo")
+		} else {
+			p.NewPage(c.W, c.H)
+		}
+		c.RenderTo(p)
+	}
+	if p == nil {
+		return fmt.Errorf("failed to render any page")
+	}
+	if err := p.Close(); err != nil {
+		return err
+	}
+	_, err = writer.Write(replacePDFProducer(buf.Bytes()))
+	return err
+}