feat(渲染能力): 支持文字裁剪，完善字体统计

ofdgo_renderer_clip.go

@@ -0,0 +1,65 @@
+// 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 (
+	"image"
+
+	"github.com/tdewolff/canvas"
+)
+
+// clipRenderer 收集图形和文字的绘制轮廓
+type clipRenderer struct {
+	path *canvas.Path
+	clip *canvas.Path
+}
+
+// Size 返回不限定边界的裁剪画布尺寸
+// 返回: float64 宽度, float64 高度
+func (r *clipRenderer) Size() (float64, float64) {
+	return 0, 0
+}
+
+// RenderPath 合并路径填充及描边轮廓
+// 入参: path 路径, style 绘制样式, m 变换矩阵
+func (r *clipRenderer) RenderPath(path *canvas.Path, style canvas.Style, m canvas.Matrix) {
+	if style.HasFill() {
+		r.add(applyClipPath(path.Copy().Transform(m), r.clip))
+	}
+	if style.HasStroke() {
+		p := path.Dash(style.DashOffset, style.Dashes...).Stroke(style.StrokeWidth, style.StrokeCapper, style.StrokeJoiner, canvas.Tolerance)
+		r.add(applyClipPath(p.Transform(m), r.clip))
+	}
+}
+
+// add 合并裁剪轮廓
+// 入参: path 裁剪路径
+func (r *clipRenderer) add(path *canvas.Path) {
+	if r.path == nil {
+		r.path = path
+	} else {
+		r.path = unionClipPath(r.path, path)
+	}
+}
+
+// RenderText 合并文字字形轮廓
+// 入参: text 文字, m 变换矩阵
+func (r *clipRenderer) RenderText(text *canvas.Text, m canvas.Matrix) {
+	text.RenderTo(r, m, 0)
+}
+
+// RenderImage 裁剪区不包含图像对象
+// 入参: img 图像, m 变换矩阵
+func (r *clipRenderer) RenderImage(img image.Image, m canvas.Matrix) {}