feat(性能优化): 优化PDF字形复用，降低多页导出耗时与内存分配

ofdgo_renderer_output.go

@@ -244,13 +244,14 @@ func (r *Renderer) renderPDFPages(pages []pdfPage, writer io.Writer) error {
 	}
 	start := buf.Len()
 	p := pdf.New(buf, pages[0].Box.W, pages[0].Box.H, nil)
+	renderer := &pdfRenderer{PDF: p, glyphPaths: make(map[*canvas.Path]*canvas.Path)}
 	p.SetInfo("", "", "", "", "xiaoqidun/ofdgo")
 	for i, page := range pages {
 		if i > 0 {
 			p.NewPage(page.Box.W, page.Box.H)
 		}
 		navigation.apply(p, i)
-		if err := r.renderPageToContext(canvas.NewContext(p), page.Content, true); err != nil {
+		if err := r.renderPageToContext(canvas.NewContext(renderer), page.Content, true); err != nil {
 			buf.Truncate(start)
 			return fmt.Errorf("failed to render page %d: %w", i+1, err)
 		}

ofdgo_renderer_pdf.go

@@ -21,6 +21,27 @@ import (
 	"github.com/tdewolff/canvas/renderers/pdf"
 )
 
+// pdfRenderer PDF渲染器
+type pdfRenderer struct {
+	*pdf.PDF
+	glyphPaths map[*canvas.Path]*canvas.Path
+}
+
+// glyphPath 复用相似变换下的PDF字形圆弧转换
+// 入参: path 缓存字形路径, matrix 字形变换
+// 返回: *canvas.Path PDF字形路径
+func (r *pdfRenderer) glyphPath(path *canvas.Path, matrix canvas.Matrix) *canvas.Path {
+	if !matrix.IsSimilarity() {
+		return path
+	}
+	if cached, ok := r.glyphPaths[path]; ok {
+		return cached
+	}
+	converted := path.ReplaceArcs()
+	r.glyphPaths[path] = converted
+	return converted
+}
+
 // pdfPage PDF页面数据
 type pdfPage struct {
 	Content *PageContent

ofdgo_renderer_text.go

@@ -396,6 +396,11 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 							scaleX = advanceLimit / glyphWidth
 						}
 						textWidth = glyphWidth * scaleX
+						if face.FauxBold != 0 {
+							if renderer, ok := ctx.Renderer.(*pdfRenderer); ok {
+								glyphPath = renderer.glyphPath(glyphPath, ctx.View().Scale(scaleX, 1))
+							}
+						}
 						if scaleX != 1 {
 							ctx.Push()
 							ctx.Translate(x, y)