feat(归并文件): 归并文件下沉通用能力

ofdgo_renderer_state_canvas.go

@@ -15,7 +15,10 @@
 package ofdgo
 
 import (
+	"crypto/sha256"
+	"encoding/binary"
 	"image"
+	"math"
 
 	"github.com/tdewolff/canvas"
 	basefont "github.com/xiaoqidun/ofdgo/internal/base/font"
@@ -152,3 +155,50 @@ func (s *canvasBackendState) resetFonts() {
 	s.textGlyphPathCache = renderCache[textGlyphPathCacheKey, textGlyphPathCacheValue]{limit: 16 << 20}
 	s.fontOutlines = make(map[*canvas.Font]*basefont.Outliner)
 }
+
+// canvasGeometryDigest 按完整坐标、路径顺序及几何容差计算摘要
+// 入参: paths 非空路径序列
+// 返回: [32]byte 几何摘要
+func canvasGeometryDigest(paths ...*canvas.Path) [32]byte {
+	hash := sha256.New()
+	var data [512]byte
+	binary.LittleEndian.PutUint64(data[:8], math.Float64bits(canvas.Tolerance))
+	binary.LittleEndian.PutUint64(data[8:16], math.Float64bits(canvas.Epsilon))
+	binary.LittleEndian.PutUint64(data[16:24], math.Float64bits(canvas.BentleyOttmannEpsilon))
+	hash.Write(data[:24])
+	for _, path := range paths {
+		values := path.Data()
+		binary.LittleEndian.PutUint64(data[:8], uint64(len(values)))
+		hash.Write(data[:8])
+		for len(values) > 0 {
+			count := min(len(values), len(data)/8)
+			for i, value := range values[:count] {
+				binary.LittleEndian.PutUint64(data[i*8:], math.Float64bits(value))
+			}
+			hash.Write(data[:count*8])
+			values = values[count:]
+		}
+	}
+	var key [32]byte
+	hash.Sum(key[:0])
+	return key
+}
+
+// settleCanvasPath 复用复杂路径的填充规范化结果，返回独立副本
+// 入参: path 页面坐标路径, rule 填充规则
+// 返回: *canvas.Path 规范化填充轮廓
+func (r *Renderer) settleCanvasPath(path *canvas.Path, rule canvas.FillRule) *canvas.Path {
+	if len(path.Data()) < 256 {
+		return path.Settle(rule)
+	}
+	key := canvasFillKey{digest: canvasGeometryDigest(path), rule: rule}
+	cache := r.canvasSettledPaths()
+	if result, ok := cache.get(key); ok {
+		return result.Copy()
+	}
+	result := path.Settle(rule)
+	if cost := len(result.Data())*8 + 256; cost <= cache.limit {
+		cache.put(key, result.Copy(), cost)
+	}
+	return result
+}