feat(后端结构): 完善多后端解耦，清理遗留代码

ofdgo_text_position.go

@@ -0,0 +1,68 @@
+// 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
+
+// TextPositioner 按OFD坐标及增量定位连续字形，不依赖字体或绘图库
+type TextPositioner struct {
+	xs, ys, dxs, dys []float64
+	direction        Point
+	current          Point
+	previous         float64
+	index            int
+}
+
+// NewTextPositioner 创建单个TextCode的定位器，方向采用OFD角度
+// 入参: code 文本定位数据, direction 阅读方向
+// 返回: TextPositioner 字形定位器
+func NewTextPositioner(code TextCode, direction int) TextPositioner {
+	result := TextPositioner{xs: parseFloats(code.X), ys: parseFloats(code.Y), dxs: parseFloats(code.DeltaX), dys: parseFloats(code.DeltaY), direction: Point{X: 1}}
+	switch direction {
+	case 90:
+		result.direction = Point{Y: 1}
+	case 180:
+		result.direction = Point{X: -1}
+	case 270:
+		result.direction = Point{Y: -1}
+	}
+	return result
+}
+
+// Next 返回下一个字形位置并保存其推进长度，显式坐标和增量优先
+// 入参: advance 当前字形推进长度，单位为毫米
+// 返回: Point 字形原点
+func (p *TextPositioner) Next(advance float64) Point {
+	i := p.index
+	if i < len(p.xs) {
+		p.current.X = p.xs[i]
+	} else if i > 0 {
+		if dx, ok := textDelta(p.dxs, i-1); ok {
+			p.current.X += dx
+		} else if len(p.dys) == 0 {
+			p.current.X += p.previous * p.direction.X
+		}
+	}
+	if i < len(p.ys) {
+		p.current.Y = p.ys[i]
+	} else if i > 0 {
+		if dy, ok := textDelta(p.dys, i-1); ok {
+			p.current.Y += dy
+		} else if len(p.dxs) == 0 {
+			p.current.Y += p.previous * p.direction.Y
+		}
+	}
+	p.previous = advance
+	p.index++
+	return p.current
+}