feat(后端架构): 完善后端解耦

ofdgo_render_preview.go

@@ -0,0 +1,57 @@
+// 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"
+	"crypto/sha256"
+	"fmt"
+	"io"
+)
+
+// PreviewOptions 指定页面显示方式，光栅预览不提供SVG对象分组
+type PreviewOptions struct {
+	Raster  bool
+	Objects bool
+}
+
+// RenderPreview 生成统一SVG容器及独立资源，原生程序与WebUI使用相同绘制入口
+// 入参: page 页面内容, writer 输出流, options 显示方式
+// 返回: SVGResources 需由调用方映射地址的资源, error 错误信息
+func (r *Renderer) RenderPreview(page *PageContent, writer io.Writer, options PreviewOptions) (SVGResources, error) {
+	if !options.Raster {
+		if options.Objects {
+			return r.RenderToSVGWithObjects(page, writer)
+		}
+		return r.RenderToSVGWithResources(page, writer)
+	}
+	if options.Objects {
+		return SVGResources{}, fmt.Errorf("raster preview does not provide SVG object groups")
+	}
+	box, err := r.GetPageBox(page)
+	if err != nil {
+		return SVGResources{}, err
+	}
+	var pixels bytes.Buffer
+	if err := r.RenderToPNG(page, &pixels); err != nil {
+		return SVGResources{}, err
+	}
+	name := fmt.Sprintf("ofdgo-image-%x", sha256.Sum256(pixels.Bytes()))
+	_, err = fmt.Fprintf(writer, `<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="%gmm" height="%gmm" viewBox="0 0 %g %g"><image width="%g" height="%g" preserveAspectRatio="none" xlink:href="%s"/></svg>`, box.W, box.H, box.W, box.H, box.W, box.H, name)
+	if err != nil {
+		return SVGResources{}, err
+	}
+	return SVGResources{Images: []SVGImage{{Name: name, MIME: "image/png", Data: pixels.Bytes()}}}, nil
+}