feat(内存占用): 降低复杂文档阅读的内存占用

ofdgo_renderer_svg.go

@@ -15,12 +15,17 @@
 package ofdgo
 
 import (
+	"bufio"
+	"bytes"
 	"crypto/sha256"
 	"fmt"
+	"image"
+	"image/png"
 	"io"
 	"strings"
 
 	"github.com/tdewolff/canvas"
+	canvasimage "github.com/tdewolff/canvas/image"
 	"github.com/tdewolff/canvas/renderers/svg"
 )
 
@@ -32,38 +37,114 @@ type SVGFont struct {
 	Data   []byte
 }
 
-// svgFontRenderer 分离字体资源的SVG渲染器
-type svgFontRenderer struct {
+// SVGImage SVG引用的图片资源，Name为图片地址，Data为只读图片数据
+type SVGImage struct {
+	Name string
+	MIME string
+	Data []byte
+}
+
+// SVGResources SVG引用的字体和图片资源
+type SVGResources struct {
+	Fonts  []SVGFont
+	Images []SVGImage
+}
+
+// svgResourceRenderer 分离外部资源的SVG渲染器
+type svgResourceRenderer struct {
 	*svg.SVG
-	renderer *Renderer
-	fonts    []SVGFont
-	seen     map[string]bool
-	styles   strings.Builder
+	renderer   *Renderer
+	writer     io.Writer
+	fonts      []SVGFont
+	images     []SVGImage
+	imageNames map[image.Image]string
+	seen       map[string]bool
+	styles     strings.Builder
+	err        error
 }
 
 // RenderToSVGWithFonts 渲染为SVG并返回页面引用的字体资源，不在SVG中嵌入字体
 // 入参: page 页面内容, writer 输出流
 // 返回: []SVGFont 字体资源，可按Name复用并按Weight、Style注册，error 错误信息
 func (r *Renderer) RenderToSVGWithFonts(page *PageContent, writer io.Writer) ([]SVGFont, error) {
+	resources, err := r.renderSVGResources(page, writer, false)
+	return resources.Fonts, err
+}
+
+// RenderToSVGWithResources 渲染为SVG并分离字体和图片，调用方需注册字体并将图片Name映射为可访问地址
+// 入参: page 页面内容, writer 输出流
+// 返回: SVGResources 可跨页面复用的资源, error 错误信息
+func (r *Renderer) RenderToSVGWithResources(page *PageContent, writer io.Writer) (SVGResources, error) {
+	return r.renderSVGResources(page, writer, true)
+}
+
+// renderSVGResources 渲染SVG并收集外部资源
+// 入参: page 页面内容, writer 输出流, images 是否分离图片
+// 返回: SVGResources 外部资源, error 错误信息
+func (r *Renderer) renderSVGResources(page *PageContent, writer io.Writer, images bool) (SVGResources, error) {
 	c, err := r.renderPage(page)
 	if err != nil {
-		return nil, err
+		return SVGResources{}, err
 	}
 	options := svg.DefaultOptions
 	options.EmbedFonts = false
-	s := &svgFontRenderer{
-		SVG:      svg.New(writer, c.W, c.H, &options),
+	buffer := bufio.NewWriter(writer)
+	s := &svgResourceRenderer{
+		SVG:      svg.New(buffer, c.W, c.H, &options),
 		renderer: r,
+		writer:   buffer,
 		seen:     make(map[string]bool),
 	}
+	if images {
+		s.imageNames = make(map[image.Image]string)
+	}
 	c.RenderTo(s)
+	if s.err != nil {
+		return SVGResources{}, s.err
+	}
 	s.SetCustomStyle(s.styles.String())
-	return s.fonts, s.Close()
+	if err := s.Close(); err != nil {
+		return SVGResources{}, err
+	}
+	return SVGResources{Fonts: s.fonts, Images: s.images}, buffer.Flush()
+}
+
+// RenderImage 绘制图片，分离资源时保持原始编码、尺寸和变换
+// 入参: img 图片对象, m 变换矩阵
+func (s *svgResourceRenderer) RenderImage(img image.Image, m canvas.Matrix) {
+	if s.imageNames == nil {
+		s.SVG.RenderImage(img, m)
+		return
+	}
+	name, ok := s.imageNames[img]
+	if !ok {
+		resource := SVGImage{MIME: "image/png"}
+		if encoded, ok := img.(*canvasimage.Image); ok {
+			resource.MIME, resource.Data = encoded.Mimetype, encoded.Bytes
+		} else {
+			var buffer bytes.Buffer
+			if err := png.Encode(&buffer, img); err != nil {
+				s.err = err
+				return
+			}
+			resource.Data = buffer.Bytes()
+		}
+		name = fmt.Sprintf("ofdgo-image-%x", sha256.Sum256(resource.Data))
+		resource.Name = name
+		s.imageNames[img] = name
+		if !s.seen[name] {
+			s.seen[name] = true
+			s.images = append(s.images, resource)
+		}
+	}
+	_, height := s.Size()
+	size := img.Bounds().Size()
+	fmt.Fprintf(s.writer, `<image transform="%s" width="%d" height="%d" xlink:href="%s"/>`, m.Translate(0, float64(size.Y)).ToSVG(height), size.X, size.Y, name)
 }
 
 // RenderText 绘制文字并记录实际使用的字体资源
 // 入参: text 文字对象, m 变换矩阵
-func (s *svgFontRenderer) RenderText(text *canvas.Text, m canvas.Matrix) {
+func (s *svgResourceRenderer) RenderText(text *canvas.Text, m canvas.Matrix) {
 	if text.Empty() {
 		return
 	}