feat(后端架构): 优化多后端渲染，修复描边与字形校验

ofdgo_renderer_gg.go

@@ -18,34 +18,39 @@ import (
 	"fmt"
 	"image"
 	"image/color"
+	"sync"
 
 	"github.com/gogpu/gg"
 )
 
 // GGBackend 提供字体、页面编译和CPU绘制，不注册全局GPU设备或隐式切换后端
-type GGBackend struct{}
+// StrokeGeometry用于GG暂不能准确处理的尖角连接、闭合或曲线虚线及亚像素渐变描边，未配置时返回能力错误
+type GGBackend struct{ StrokeGeometry GeometryBackend }
 
 // Name 返回后端标识
 // 返回: string 后端标识
 func (GGBackend) Name() string { return "gg" }
 
-// Render 绘制已编译页面，使用自有双圆渐变语义保持原有定位
+// Prepare 将路径、样式和裁剪准备为固定DPI的GG场景
 // 入参: page 只读页面
-// 返回: image.Image 图像, error 绘制错误
-func (GGBackend) Render(page *RasterPage) (image.Image, error) {
+// 返回: RasterScene 可重复绘制场景, error 准备错误
+func (b GGBackend) Prepare(page *RasterPage) (RasterScene, error) {
 	w, h, err := page.PixelSize()
 	if err != nil {
 		return nil, err
 	}
-	pixmap := gg.NewPixmap(w, h)
-	img := pixmap.ImageView()
-	raster := gg.NewSoftwareRenderer(w, h)
+	page = cloneRasterPage(page)
+	scene := &ggRasterScene{page: page, width: w, height: h, masks: renderCache[[32]byte, *image.Alpha]{limit: 16 << 20}}
 	for i, cmd := range page.Commands {
+		if cmd.Stroke != nil && !ggNativeStroke(cmd, page.DPI/25.4) {
+			cmd, err = b.expandStroke(cmd)
+			if err != nil {
+				return nil, fmt.Errorf("gg command %d: %w", i, err)
+			}
+		}
 		m := page.PixelTransform(cmd.Transform, h)
 		if cmd.Image != nil {
-			if err := drawRasterImageCommand(GGBackend{}, page, img, imagePixelSource(cmd.Image), cmd); err != nil {
-				return nil, err
-			}
+			scene.commands = append(scene.commands, ggRasterCommand{command: cmd})
 			continue
 		}
 		path := gg.NewPath()
@@ -81,16 +86,119 @@ func (GGBackend) Render(page *RasterPage) (image.Image, error) {
 				return ggRGBA(g.At(p.X, p.Y))
 			}))
 		}
-		if cmd.EvenOdd {
+		if cmd.EvenOdd && cmd.Stroke == nil {
 			paint.FillRule = gg.FillRuleEvenOdd
 		}
-		if err := raster.Fill(pixmap, path, paint); err != nil {
+		if cmd.Clip != nil {
+			mask, err := rasterClipMask(GGBackend{}, page, cmd.Clip, &scene.masks)
+			if err != nil {
+				return nil, err
+			}
+			if mask.Rect.Empty() {
+				continue
+			}
+			paint.ClipMask, paint.ClipMaskW, paint.ClipMaskH = mask.Pix, mask.Stride, mask.Rect.Dy()
+			paint.ClipMaskX, paint.ClipMaskY = mask.Rect.Min.X, mask.Rect.Min.Y
+		}
+		if cmd.Stroke != nil {
+			style, err := ggStroke(*cmd.Stroke, page.DPI/25.4)
+			if err != nil {
+				return nil, err
+			}
+			paint.SetStroke(style)
+			paint.SetStrokeBrush(paint.FillBrush())
+		}
+		scene.commands = append(scene.commands, ggRasterCommand{command: cmd, path: path, paint: paint})
+	}
+	return scene, nil
+}
+
+// ggRasterCommand 保存已转换的像素路径和样式
+type ggRasterCommand struct {
+	command RasterCommand
+	path    *gg.Path
+	paint   *gg.Paint
+}
+
+// ggRasterScene 复用路径和局部裁剪，串行保护掩码缓存
+type ggRasterScene struct {
+	mu            sync.Mutex
+	page          *RasterPage
+	width, height int
+	commands      []ggRasterCommand
+	masks         renderCache[[32]byte, *image.Alpha]
+}
+
+// Render 绘制独立像素缓冲，不累积上次内容
+// 返回: image.Image 图像, error 绘制错误
+func (s *ggRasterScene) Render() (image.Image, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	pixmap := gg.NewPixmap(s.width, s.height)
+	img := pixmap.ImageView()
+	raster := gg.NewSoftwareRenderer(s.width, s.height)
+	for i, cmd := range s.commands {
+		var err error
+		switch {
+		case cmd.command.Image != nil:
+			err = drawRasterImageCommand(GGBackend{}, s.page, img, imagePixelSource(cmd.command.Image), cmd.command, &s.masks)
+		case cmd.command.Stroke != nil:
+			err = raster.Stroke(pixmap, cmd.path, cmd.paint)
+		default:
+			err = raster.Fill(pixmap, cmd.path, cmd.paint)
+		}
+		if err != nil {
 			return nil, fmt.Errorf("gg command %d: %w", i, err)
 		}
 	}
 	return img, nil
 }
 
+// Render 准备并绘制页面，重复绘制可使用Prepare复用场景
+// 入参: page 只读页面
+// 返回: image.Image 图像, error 绘制错误
+func (b GGBackend) Render(page *RasterPage) (image.Image, error) {
+	scene, err := b.Prepare(page)
+	if err != nil {
+		return nil, err
+	}
+	return scene.Render()
+}
+
+// ggStroke 将页面毫米样式转换为GG像素描边，虚线与线宽同步换算
+// 入参: options 描边样式, scale 每毫米像素数
+// 返回: gg.Stroke 像素样式, error 样式错误
+func ggStroke(options StrokeOptions, scale float64) (gg.Stroke, error) {
+	if err := validateStroke(options); err != nil {
+		return gg.Stroke{}, err
+	}
+	style := gg.DefaultStroke().WithWidth(options.Width * scale)
+	style.MiterLimit = options.MiterLimit
+	if style.MiterLimit == 0 {
+		style.MiterLimit = defaultMiterLimit
+	}
+	switch options.Cap {
+	case "Round":
+		style.Cap = gg.LineCapRound
+	case "Square":
+		style.Cap = gg.LineCapSquare
+	}
+	switch options.Join {
+	case "Round":
+		style.Join = gg.LineJoinRound
+	case "Bevel":
+		style.Join = gg.LineJoinBevel
+	}
+	if len(options.Dashes) > 0 {
+		dashes := make([]float64, len(options.Dashes))
+		for i, value := range options.Dashes {
+			dashes[i] = value * scale
+		}
+		style = style.WithDashPattern(dashes...).WithDashOffset(options.DashOffset * scale)
+	}
+	return style, nil
+}
+
 // ggRGBA 将标准库预乘颜色转换为gg的非预乘颜色
 // 入参: c 预乘颜色
 // 返回: gg.RGBA 非预乘颜色