feat(渲染引擎): 修复文字渲染并优化图像处理

ofdgo_renderer_pdf_canvas.go

@@ -16,6 +16,7 @@ package ofdgo
 
 import (
 	"fmt"
+	"image"
 
 	"github.com/tdewolff/canvas"
 	"github.com/tdewolff/canvas/renderers/pdf"
@@ -54,6 +55,16 @@ type pdfOutline struct {
 	Y     float64
 }
 
+// RenderImage 在图像局部保存状态前同步不透明画笔，避免恢复后的透明度与后端缓存不一致
+// 入参: img 图像, matrix 图像变换
+func (r *pdfRenderer) RenderImage(img image.Image, matrix canvas.Matrix) {
+	style := canvas.DefaultStyle
+	style.Fill = canvas.Paint{Color: canvas.White}
+	style.Stroke = canvas.Paint{Color: canvas.Black}
+	r.PDF.RenderPath(&canvas.Path{}, style, canvas.Identity)
+	r.PDF.RenderImage(img, matrix)
+}
+
 // 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