feat(后端架构): 完善后端解耦

ofdgo_renderer_page_canvas.go

@@ -0,0 +1,95 @@
+// 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 (
+	"github.com/tdewolff/canvas"
+)
+
+// renderCanvasPage 渲染特定页面内容
+// 入参: page 页面内容
+// 返回: *canvas.Canvas 画布实例, error 错误信息
+func (r *Renderer) renderCanvasPage(page *PageContent) (*canvas.Canvas, error) {
+	box, err := r.GetPageBox(page)
+	if err != nil {
+		return nil, err
+	}
+	width, height := box.W, box.H
+	c := canvas.New(width, height)
+	ctx := canvas.NewContext(c)
+	if err := r.renderCanvasPageToContext(ctx, page, !r.TransparentBackground); err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// renderCanvasContext 渲染页面到默认解释器上下文
+// 入参: ctx 画布上下文, page 页面内容
+// 返回: error 错误信息
+func (r *Renderer) renderCanvasContext(ctx *canvas.Context, page *PageContent) error {
+	renderer := *r
+	renderer.decodeImages = true
+	return renderer.renderCanvasPageToContext(ctx, page, !r.TransparentBackground)
+}
+
+// renderCanvasPageToContext 渲染页面到指定上下文
+// 入参: ctx 画布上下文, page 页面内容, drawBackground 是否绘制页面背景
+// 返回: error 错误信息
+func (r *Renderer) renderCanvasPageToContext(ctx *canvas.Context, page *PageContent, drawBackground bool) error {
+	r.renderError = nil
+	box, err := r.GetPageBox(page)
+	if err != nil {
+		return err
+	}
+	if r.OnPageText != nil {
+		renderer := *r
+		renderer.pageText = &PageText{}
+		r = &renderer
+	}
+	pageH := box.H
+	if drawBackground {
+		ctx.SetFillColor(canvas.White)
+		ctx.DrawPath(0, 0, canvas.Rectangle(box.W, box.H))
+	}
+	for order := range 3 {
+		if r.Reader.doc != nil {
+			for _, tplRef := range page.Template {
+				kind := tplRef.ZOrder
+				if kind == "" {
+					kind = "Background"
+				}
+				if layerOrder(kind) == order {
+					r.renderTemplate(ctx, tplRef.TemplateID, pageH)
+				}
+			}
+		}
+		r.renderLayers(ctx, page.Content.Layer, pageH, order)
+	}
+	if r.RenderAnnotations {
+		r.renderAnnotations(ctx, page.ID, pageH)
+	}
+	if stamps, ok := r.Reader.Stamps[page.ID]; ok {
+		for _, stamp := range stamps {
+			r.renderStamp(ctx, stamp, pageH)
+		}
+	}
+	if r.renderError != nil {
+		return r.renderError
+	}
+	if r.OnPageText != nil {
+		r.OnPageText(page, r.pageText)
+	}
+	return nil
+}