feat(签名验证): 完善签名验证功能

ofdgo_renderer_stamp.go

@@ -18,16 +18,23 @@ import (
 	"bytes"
 	"image"
 	"image/color"
+	"image/draw"
+	"math"
 
 	"github.com/tdewolff/canvas"
+	"github.com/tdewolff/canvas/renderers/rasterizer"
 )
 
 // 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 {
+		if s.Clip != nil {
+			if img := r.renderOFDStampImage(s.Data); img != nil {
+				r.renderStampImage(ctx, stampImageWithTransparentWhite(img), s, pageH)
+			}
+			return
+		}
 		reader, err := NewReader(bytes.NewReader(s.Data), int64(len(s.Data)))
 		if err == nil {
 			defer reader.Close()
@@ -44,8 +51,8 @@ func (r *Renderer) renderStamp(ctx *canvas.Context, s Stamp, pageH float64) {
 						continue
 					}
 					ctx.Push()
-					ctx.Translate(x, screenY)
-					ctx.Scale(w/sealBox.W, h/sealBox.H)
+					ctx.Translate(s.Box.X, pageH-(s.Box.Y+s.Box.H))
+					ctx.Scale(s.Box.W/sealBox.W, s.Box.H/sealBox.H)
 					renderer.renderPageToContext(ctx, content, false)
 					ctx.Pop()
 				}
@@ -56,17 +63,76 @@ func (r *Renderer) renderStamp(ctx *canvas.Context, s Stamp, pageH float64) {
 	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()
+			r.renderStampImage(ctx, stampImageWithTransparentWhite(img), s, pageH)
 			return
 		}
 	}
 }
 
+// renderOFDStampImage 渲染OFD印章图像
+// 入参: data OFD印章数据
+// 返回: image.Image 印章图像
+func (r *Renderer) renderOFDStampImage(data []byte) image.Image {
+	reader, err := NewReader(bytes.NewReader(data), int64(len(data)))
+	if err != nil {
+		return nil
+	}
+	defer reader.Close()
+	doc, err := reader.Doc()
+	if err != nil {
+		return 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
+		}
+		c := canvas.New(sealBox.W, sealBox.H)
+		if err := renderer.renderPageToContext(canvas.NewContext(c), content, false); err != nil {
+			continue
+		}
+		return rasterizer.Draw(c, canvas.DPMM(r.DPI/25.4), canvas.DefaultColorSpace)
+	}
+	return nil
+}
+
+// renderStampImage 渲染印章图像
+// 入参: ctx 画布上下文, img 印章图像, s 印章对象, pageH 页面高度
+func (r *Renderer) renderStampImage(ctx *canvas.Context, img image.Image, s Stamp, pageH float64) {
+	box := s.Box
+	if s.Clip != nil {
+		img = clipStampImage(img, box, *s.Clip)
+		box.X += s.Clip.X
+		box.Y += s.Clip.Y
+		box.W = s.Clip.W
+		box.H = s.Clip.H
+	}
+	ctx.Push()
+	ctx.Translate(box.X, pageH-(box.Y+box.H))
+	ctx.Scale(box.W/float64(img.Bounds().Dx()), box.H/float64(img.Bounds().Dy()))
+	ctx.DrawImage(0, 0, img, canvas.DPMM(1.0))
+	ctx.Pop()
+}
+
+// clipStampImage 裁剪印章图像
+// 入参: img 印章图像, box 印章区域, clip 裁剪区域
+// 返回: image.Image 裁剪后的印章图像
+func clipStampImage(img image.Image, box, clip Box) image.Image {
+	bounds := img.Bounds()
+	x0 := int(math.Floor(clip.X / box.W * float64(bounds.Dx())))
+	y0 := int(math.Floor(clip.Y / box.H * float64(bounds.Dy())))
+	x1 := int(math.Ceil((clip.X + clip.W) / box.W * float64(bounds.Dx())))
+	y1 := int(math.Ceil((clip.Y + clip.H) / box.H * float64(bounds.Dy())))
+	out := image.NewNRGBA(image.Rect(0, 0, x1-x0, y1-y0))
+	draw.Draw(out, out.Bounds(), img, image.Pt(bounds.Min.X+x0, bounds.Min.Y+y0), draw.Src)
+	return out
+}
+
 // 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