refactor(重构代码): 拆分代码，提升代码质量

ofdgo_renderer_stamp.go

@@ -0,0 +1,102 @@
+// 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"
+	"image"
+	"image/color"
+
+	"github.com/tdewolff/canvas"
+)
+
+// renderStamp 渲染印章
+// 入参: ctx 画布上下文, s 印章对象, pageH 页面高度
+func (r *Renderer) renderStamp(ctx *canvas.Context, s Stamp, pageH float64) {
+	x, y, w, h := s.Box.X, s.Box.Y, s.Box.W, s.Box.H
+	screenY := pageH - (y + h)
+	if s.Type == "ofd" && len(s.Data) > 0 {
+		reader, err := NewReader(bytes.NewReader(s.Data), int64(len(s.Data)))
+		if err == nil {
+			defer reader.Close()
+			doc, err := reader.Doc()
+			if err == nil {
+				renderer := r.childRenderer(reader)
+				for _, pageRef := range doc.Pages.Page {
+					content, err := reader.PageContent(pageRef)
+					if err != nil {
+						continue
+					}
+					sealBox, err := renderer.GetPageBox(content)
+					if err != nil {
+						continue
+					}
+					ctx.Push()
+					ctx.Translate(x, screenY)
+					ctx.Scale(w/sealBox.W, h/sealBox.H)
+					renderer.renderPageToContext(ctx, content, false)
+					ctx.Pop()
+				}
+				return
+			}
+		}
+	}
+	if len(s.Data) > 0 {
+		img, _, err := decodeImageData(s.Data)
+		if err == nil {
+			img = stampImageWithTransparentWhite(img)
+			ctx.Push()
+			ctx.Translate(x, screenY)
+			ctx.Scale(w/float64(img.Bounds().Dx()), h/float64(img.Bounds().Dy()))
+			ctx.DrawImage(0, 0, img, canvas.DPMM(1.0))
+			ctx.Pop()
+			return
+		}
+	}
+}
+
+// stampImageWithTransparentWhite 处理印章图片白色底色
+// 入参: img 印章图片对象
+// 返回: image.Image 处理后的印章图片对象
+func stampImageWithTransparentWhite(img image.Image) image.Image {
+	if opaque, ok := img.(interface{ Opaque() bool }); ok && !opaque.Opaque() {
+		return img
+	}
+	bounds := img.Bounds()
+	out := image.NewNRGBA(bounds)
+	hasAlpha := false
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			c := color.NRGBAModel.Convert(img.At(x, y)).(color.NRGBA)
+			if c.A < 255 {
+				hasAlpha = true
+			}
+			out.SetNRGBA(x, y, c)
+		}
+	}
+	if hasAlpha {
+		return img
+	}
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			c := out.NRGBAAt(x, y)
+			if c.R >= 250 && c.G >= 250 && c.B >= 250 {
+				c.A = 0
+				out.SetNRGBA(x, y, c)
+			}
+		}
+	}
+	return out
+}