feat(渲染引擎): 修复文字渲染并优化图像处理

go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/tdewolff/canvas v0.0.0-20260923214215-09804640d00c
 	github.com/tdewolff/font v0.0.0-20260913163313-54f98bb59ee6
 	github.com/xiaoqidun/jbig2 v1.1.1
-	github.com/xiaoqidun/pdfgo v0.0.0-20261002164637-41541220b1c3
+	github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58
 	golang.org/x/crypto v0.57.0
 	golang.org/x/image v0.46.0
 	golang.org/x/text v0.42.0

go.sum

@@ -62,8 +62,8 @@ github.com/tdewolff/test v1.0.12 h1:7F21DqIajswxuche0geHdrUZRCWE4oko4b7bcmkkrxk=
 github.com/tdewolff/test v1.0.12/go.mod h1:XPuWBzvdUzhCuxWO1ojpXsyzsA5bFoS3tO/Q3kFuTG8=
 github.com/xiaoqidun/jbig2 v1.1.1 h1:SjliS9ZO0e9HX5oYUfBuXrfFsXhWricrSz+XY4zORDI=
 github.com/xiaoqidun/jbig2 v1.1.1/go.mod h1:8QonVWtENmh2kc6l+leqeGl7psb79DWlHDkCpdChjfQ=
-github.com/xiaoqidun/pdfgo v0.0.0-20261002164637-41541220b1c3 h1:mrWCBsxLuBf1sjeEK9r+1KZa5WpER5J3sDPVicajM1E=
+github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58 h1:n2RFxdeo5fmtvgkRKeMSgJHqmVEGMoS45SppUk4laaE=
-github.com/xiaoqidun/pdfgo v0.0.0-20261002164637-41541220b1c3/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
+github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
 github.com/yuin/goldmark v1.8.5 h1:r6N5afV5qj/5S4UTch8agZHJ8UxNCMwX7WjkkJam2NA=

ofdgo_editor_text.go

@@ -138,6 +138,7 @@ func (e *Editor) UpdateTextContent(page int, id, value string, style TextStyle)
 // RewriteText 保留原文的字形定位，不修改对象样式或文档
 // 等长替换保留各字原位；单段增删保留前缀和后缀步进，新增字符沿用局部字距
 // 方向、缩放和修饰原样保留；复杂布局仅支持等长替换，合并字形需显式重排
+// 首段缺失坐标仅在临时校验中恢复，不改写源坐标
 // 入参: obj 原文字对象, value 新内容
 // 返回: error 错误信息
 func (e *Editor) RewriteText(obj *TextObject, value string) error {
@@ -147,6 +148,7 @@ func (e *Editor) RewriteText(obj *TextObject, value string) error {
 	}
 	check := cloneEditorData(*obj)
 	check.VScale, check.Decoration = 0, ""
+	check.TextCode = textCodeOrigins(check.TextCode, 0)
 	if err := e.prepareText(&check); err != nil {
 		var missing *MissingGlyphError
 		if !errors.As(err, &missing) {

ofdgo_image.go

@@ -436,7 +436,7 @@ func imageNRGBAAt(img image.Image, x, y int) color.NRGBA {
 // 返回: color.NRGBA64 NRGBA64像素
 func imageNRGBA64At(img image.Image, x, y int) color.NRGBA64 {
 	switch src := img.(type) {
-	case *image.NRGBA64:
+	case interface{ NRGBA64At(int, int) color.NRGBA64 }:
 		return src.NRGBA64At(x, y)
 	case *image.Gray16:
 		c := src.Gray16At(x, y)

ofdgo_pdf_composite_draw.go

@@ -509,7 +509,7 @@ func (c *pdfCompositor) imageColor(mark *pdfgo.ImageMark, point pdfgo.Point, spa
 	source := c.cache.images[mark.Image]
 	if source == nil {
 		var err error
-		source, err = mark.Image.DecodeComponents()
+		source, err = mark.Image.DecodeComponentsContext(c.importer.ctx)
 		if err != nil {
 			return [4]float64{}, 0, err
 		}

ofdgo_pdf_composite_pattern.go

@@ -187,7 +187,7 @@ func (p *pdfImporter) directCompositeNode(node pdfCompositeNode, space *pdfgo.Co
 				source := p.compositingCache().images[node.image.Image]
 				if source == nil {
 					var err error
-					source, err = node.image.Image.DecodeComponents()
+					source, err = node.image.Image.DecodeComponentsContext(p.ctx)
 					if err != nil {
 						return false, err
 					}

ofdgo_pdf_object.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"image"
 	"image/color"
-	"image/png"
 	"math"
 	"strconv"
 	"unicode/utf8"
@@ -57,12 +56,19 @@ func (s *pdfStencilImage) Bounds() image.Rectangle { return s.source.Bounds() }
 // 入参: x 横向坐标, y 纵向坐标
 // 返回: color.Color 非预乘颜色
 func (s *pdfStencilImage) At(x, y int) color.Color {
+	return s.NRGBA64At(x, y)
+}
+
+// NRGBA64At 直接读取模板覆盖率，保留填充色的有效精度
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.NRGBA64 非预乘颜色
+func (s *pdfStencilImage) NRGBA64At(x, y int) color.NRGBA64 {
 	if !image.Pt(x, y).In(s.Bounds()) {
 		return color.NRGBA64{}
 	}
-	gray, _, _, _ := s.source.At(x, y).RGBA()
+	gray := imageNRGBA64At(s.source, x, y)
 	pixel := s.fill
-	pixel.A = uint16(65535 - gray)
+	pixel.A = uint16(65535 - gray.R)
 	return pixel
 }
 
@@ -112,7 +118,7 @@ func (p *pdfImporter) image(mark pdfgo.ImageMark) error {
 		}
 		var decoded image.Image
 		if len(jbig2Original) == 0 {
-			decoded, err = source.DecodeImage()
+			decoded, err = source.DecodeImageContext(p.ctx)
 			if err != nil {
 				return err
 			}
@@ -139,7 +145,7 @@ func (p *pdfImporter) image(mark pdfgo.ImageMark) error {
 		} else if len(jpegOriginal) != 0 {
 			encoded.Write(jpegOriginal)
 		} else {
-			if err := png.Encode(&encoded, decoded); err != nil {
+			if err := pdfgo.EncodePNG(p.ctx, &encoded, decoded); err != nil {
 				return err
 			}
 		}

ofdgo_raster_image.go

@@ -22,6 +22,9 @@ import (
 	"golang.org/x/image/math/f64"
 )
 
+// rasterScaleBufferLimit 限制整像素缩放器的浮点中间缓冲，超出时使用逐行采样
+const rasterScaleBufferLimit = 8 << 20
+
 // PixelTransform 将页面毫米变换转换为像素变换，保留尺寸取整后的原点位置
 // 入参: m 局部到页面变换, height 目标像素高度
 // 返回: RasterMatrix 局部到像素变换
@@ -40,7 +43,7 @@ func drawRasterImage(dst draw.Image, src image.Image, m RasterMatrix) {
 	drawRasterImagePixels(dst, src, m, draw.Over)
 }
 
-// drawRasterImagePixels 对整像素边界的轴向缩小使用可分离采样，其余变换保留通用路径
+// drawRasterImagePixels 对轴向缩小使用可分离采样，其余变换保留通用路径
 // 入参: dst 目标图像, src 源图像, m 像素变换, op 合成操作
 func drawRasterImagePixels(dst draw.Image, src image.Image, m RasterMatrix, op draw.Op) {
 	b := src.Bounds()
@@ -51,10 +54,13 @@ func drawRasterImagePixels(dst draw.Image, src image.Image, m RasterMatrix, op d
 		draw.CatmullRom.Scale(dst, dr, src, b, op, nil)
 		return
 	}
+	if drawRasterAxisImage(dst, src, m, op) {
+		return
+	}
 	draw.CatmullRom.Transform(dst, f64.Aff3{m[0], m[2], m[4], m[1], m[3], m[5]}, src, b, op, nil)
 }
 
-// rasterScaleBounds 检查变换是否可无几何取整地使用缩放器，并避开其整数溢出范围
+// rasterScaleBounds 检查变换是否可无几何取整地使用缩放器，并限制其中间缓冲
 // 入参: b 源边界, m 像素变换
 // 返回: image.Rectangle 缩放边界, bool 是否适用
 func rasterScaleBounds(b image.Rectangle, m RasterMatrix) (image.Rectangle, bool) {
@@ -68,7 +74,7 @@ func rasterScaleBounds(b image.Rectangle, m RasterMatrix) (image.Rectangle, bool
 			return image.Rectangle{}, false
 		}
 	}
-	if x1 <= x0 || y1 <= y0 || b.Dx() > math.MaxInt32 || b.Dy() > math.MaxInt32 || (x1-x0)*float64(b.Dy()) > float64(min(math.MaxInt32, int(^uint(0)>>1)/32)) {
+	if x1 <= x0 || y1 <= y0 || b.Dx() > math.MaxInt32 || b.Dy() > math.MaxInt32 || (x1-x0)*float64(b.Dy()) > rasterScaleBufferLimit/32 {
 		return image.Rectangle{}, false
 	}
 	return image.Rect(int(x0), int(y0), int(x1), int(y1)), true

ofdgo_raster_image_scale.go

@@ -0,0 +1,225 @@
+// 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"
+	"image/color"
+	"math"
+	"slices"
+
+	"golang.org/x/image/draw"
+)
+
+// rasterAxisSample 保存目标像素及其归一化源采样权重
+type rasterAxisSample struct {
+	pixel   int
+	first   int
+	weights []float64
+}
+
+// rasterImagePixel 保存未取整或裁切的预乘颜色累积值
+type rasterImagePixel struct {
+	r, g, b, a float64
+}
+
+// rasterImageRow 保存正在累积的目标行
+type rasterImageRow struct {
+	sample rasterAxisSample
+	values []rasterImagePixel
+}
+
+// rasterImageSource 为通用图片提供预乘十六位采样
+type rasterImageSource struct{ image.Image }
+
+// RGBA64At 读取通用颜色的原始预乘分量
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.RGBA64 预乘颜色
+func (s rasterImageSource) RGBA64At(x, y int) color.RGBA64 {
+	r, g, b, a := s.At(x, y).RGBA()
+	return color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)}
+}
+
+// drawRasterAxisImage 按像素中心进行轴向缩小，逐行复用横向采样并保留镜像与小数坐标
+// 入参: dst 目标图像, src 源图像, m 像素变换, op 合成操作
+// 返回: bool 是否使用轴向采样
+func drawRasterAxisImage(dst draw.Image, src image.Image, m RasterMatrix, op draw.Op) bool {
+	sx, sy := math.Abs(m[0]), math.Abs(m[3])
+	if m[1] != 0 || m[2] != 0 || sx == 0 || sy == 0 || sx > 1 || sy > 1 || sx == 1 && sy == 1 {
+		return false
+	}
+	for _, v := range m {
+		if math.IsNaN(v) || math.IsInf(v, 0) {
+			return false
+		}
+	}
+	b := src.Bounds()
+	if b.Empty() {
+		return true
+	}
+	r := rasterImageBounds(b, m, dst.Bounds())
+	if r.Empty() {
+		return true
+	}
+	xs := rasterImageAxis(r.Min.X, r.Max.X, b.Min.X, b.Max.X, m[0], m[4])
+	ys := rasterImageAxis(r.Min.Y, r.Max.Y, b.Min.Y, b.Max.Y, m[3], m[5])
+	if len(xs) == 0 || len(ys) == 0 {
+		return true
+	}
+	if m[3] < 0 {
+		slices.Reverse(ys)
+	}
+	pixels, ok := src.(image.RGBA64Image)
+	if !ok {
+		pixels = rasterImageSource{src}
+	}
+	width := len(xs)
+	horizontal := make([]rasterImagePixel, width)
+	columns := make([]int, width)
+	output := image.NewRGBA64(image.Rect(0, 0, width, 1))
+	var active []rasterImageRow
+	var free [][]rasterImagePixel
+	next := 0
+	for y := ys[0].first; next < len(ys) || len(active) != 0; y++ {
+		if len(active) == 0 && y < ys[next].first {
+			y = ys[next].first
+		}
+		for next < len(ys) && ys[next].first == y {
+			var row []rasterImagePixel
+			if n := len(free); n != 0 {
+				row, free = free[n-1], free[:n-1]
+				clear(row)
+			} else {
+				row = make([]rasterImagePixel, width)
+			}
+			active = append(active, rasterImageRow{sample: ys[next], values: row})
+			next++
+		}
+		rasterImageHorizontal(horizontal, pixels, xs, y, columns)
+		n := 0
+		for _, row := range active {
+			weight := row.sample.weights[y-row.sample.first]
+			if weight != 0 {
+				for x, value := range horizontal {
+					p := &row.values[x]
+					p.r += value.r * weight
+					p.g += value.g * weight
+					p.b += value.b * weight
+					p.a += value.a * weight
+				}
+			}
+			if y+1 == row.sample.first+len(row.sample.weights) {
+				rasterImageWriteRow(dst, output, row.values, xs[0].pixel, row.sample.pixel, op)
+				free = append(free, row.values)
+			} else {
+				active[n] = row
+				n++
+			}
+		}
+		active = active[:n]
+	}
+	return true
+}
+
+// rasterImageAxis 按连续源坐标生成CatmullRom权重，不对图像几何边界取整
+// 入参: first 目标起点, end 目标终点, source 源起点, limit 源终点, scale 缩放比例, offset 平移距离
+// 返回: []rasterAxisSample 轴向采样表
+func rasterImageAxis(first, end, source, limit int, scale, offset float64) []rasterAxisSample {
+	result := make([]rasterAxisSample, 0, end-first)
+	argument := math.Abs(scale)
+	support := draw.CatmullRom.Support / argument
+	for pixel := first; pixel < end; pixel++ {
+		center := (float64(pixel) + .5 - offset) / scale
+		if center < float64(source) || center >= float64(limit) {
+			continue
+		}
+		center -= .5
+		start := int(max(float64(source), math.Floor(center-support)))
+		stop := int(min(float64(limit), math.Ceil(center+support)))
+		weights := make([]float64, stop-start)
+		total := 0.0
+		for i := range weights {
+			distance := math.Abs((float64(start+i) - center) * argument)
+			if distance < draw.CatmullRom.Support {
+				weights[i] = draw.CatmullRom.At(distance)
+				total += weights[i]
+			}
+		}
+		for i := range weights {
+			weights[i] /= total
+		}
+		result = append(result, rasterAxisSample{pixel: pixel, first: start, weights: weights})
+	}
+	return result
+}
+
+// rasterImageHorizontal 按源列复用像素，保留各目标像素的权重累加顺序与中间精度
+// 入参: row 横向缓冲, src 源像素, samples 采样表, y 源行坐标, columns 活动列缓冲
+func rasterImageHorizontal(row []rasterImagePixel, src image.RGBA64Image, samples []rasterAxisSample, y int, columns []int) {
+	clear(row)
+	reversed := samples[0].first > samples[len(samples)-1].first
+	start, end := samples[0].first, samples[0].first+len(samples[0].weights)
+	for _, sample := range samples[1:] {
+		start = min(start, sample.first)
+		end = max(end, sample.first+len(sample.weights))
+	}
+	next, count := 0, 0
+	for x := start; x < end; x++ {
+		for next < len(samples) {
+			index := next
+			if reversed {
+				index = len(samples) - next - 1
+			}
+			if samples[index].first > x {
+				break
+			}
+			columns[count] = index
+			count++
+			next++
+		}
+		p := src.RGBA64At(x, y)
+		n := 0
+		for _, index := range columns[:count] {
+			sample := samples[index]
+			weight := sample.weights[x-sample.first]
+			if weight != 0 {
+				value := &row[index]
+				value.r += float64(p.R) * weight
+				value.g += float64(p.G) * weight
+				value.b += float64(p.B) * weight
+				value.a += float64(p.A) * weight
+			}
+			if x+1 < sample.first+len(sample.weights) {
+				columns[n] = index
+				n++
+			}
+		}
+		count = n
+	}
+}
+
+// rasterImageWriteRow 在两轴采样完成后取整并使用标准预乘合成
+// 入参: dst 目标图像, output 行像素缓冲, values 累积颜色, x 横向起点, y 目标行坐标, op 合成操作
+func rasterImageWriteRow(dst draw.Image, output *image.RGBA64, values []rasterImagePixel, x, y int, op draw.Op) {
+	for i, value := range values {
+		output.SetRGBA64(i, 0, color.RGBA64{
+			R: uint16(min(max(min(value.r, value.a)+.5, 0), 65535)),
+			G: uint16(min(max(min(value.g, value.a)+.5, 0), 65535)),
+			B: uint16(min(max(min(value.b, value.a)+.5, 0), 65535)),
+			A: uint16(min(max(value.a+.5, 0), 65535)),
+		})
+	}
+	draw.Draw(dst, image.Rect(x, y, x+len(values), y+1), output, image.Point{}, op)
+}

ofdgo_render_compile.go

@@ -324,9 +324,6 @@ func (c *semanticCompiler) objectStyle(object PathObject, defaults *DrawParam, l
 	if object.DashOffset != nil {
 		style.options.DashOffset = *object.DashOffset
 	}
-	if style.stroke == nil {
-		style.stroke = &FillColor{}
-	}
 	style.fill = withFillAlpha(style.fill, object.Alpha)
 	style.stroke = withFillAlpha(style.stroke, object.Alpha)
 	if scale := math.Sqrt(math.Abs(linear.a*linear.d - linear.b*linear.c)); scale > 0 {
@@ -379,6 +376,9 @@ func (c *semanticCompiler) pathObject(object PathObject, state RenderState) erro
 		return err
 	}
 	style := c.objectStyle(object, state.Defaults, linear)
+	if style.stroke == nil {
+		style.stroke = withFillAlpha(&FillColor{}, object.Alpha)
+	}
 	shading, _ := renderObjectMatrix(object.Boundary, IdentityMatrix, state)
 	if object.Fill != nil && *object.Fill {
 		paint, err := c.renderer.ResolvePaint(style.fill)

ofdgo_render_text.go

@@ -128,6 +128,14 @@ func (r *Renderer) PositionText(object TextObject, state RenderState) (*Position
 	}
 	ascent, descent, _ := metrics.VerticalMetrics()
 	unit := size / float64(metrics.UnitsPerEm())
+	recoverBaseline := len(object.TextCode) > 0 && object.TextCode[0].Y == ""
+	object.TextCode = textCodeOrigins(object.TextCode, float64(ascent)*unit)
+	if recoverBaseline {
+		if text := object.Text(); text != result.Run.Text {
+			result.Run.Text = text
+			result.Run.Boxes = make([]Box, len([]rune(text)))
+		}
+	}
 	transforms := r.textObjectGlyphTransforms(id, object)
 	codeOffset, textOffset := 0, 0
 	angle := float64(object.CharDirection) * math.Pi / 180

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

ofdgo_renderer_text_canvas.go

@@ -115,7 +115,7 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 		}
 		strokeStyle.applyLineJoin(obj.Join, obj.MiterLimit)
 		if strokeStyle.strokePaint == nil {
-			strokeStyle.strokePaint = colorWithAlpha(canvas.Black, obj.Alpha)
+			strokeStyle.strokePaint = canvas.Transparent
 		}
 		strokeStyle.scale(ctm)
 		if strokeStyle.lineWidth == 0 {
@@ -182,10 +182,22 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 		return
 	}
 	face := ff.Face(sizePt, fillPaint, fontStyle, canvas.FontNormal)
+	recoverBaseline := len(obj.TextCode) > 0 && obj.TextCode[0].Y == ""
 	var metrics canvas.FontMetrics
-	if textRun != nil {
+	if textRun != nil || recoverBaseline {
 		metrics = face.Metrics()
 	}
+	ascent := metrics.Ascent
+	if scale := ctm.YScale(); scale > 0 && !useTextMatrix {
+		ascent /= scale
+	}
+	obj.TextCode = textCodeOrigins(obj.TextCode, ascent)
+	if textRun != nil && recoverBaseline {
+		if text := obj.Text(); text != textRun.Text {
+			textRun.Text = text
+			textRun.Boxes = make([]Box, len([]rune(text)))
+		}
+	}
 	glyphTransforms := r.textObjectGlyphTransforms(fontID, obj)
 	hasUnderline := strings.Contains(obj.Decoration, "Underline")
 	_, shadedFill := fillPaint.(canvas.Gradient)

ofdgo_text.go

@@ -36,6 +36,7 @@ type textGlyphTransform struct {
 // Text 获取定位后的文字，横向换行以换行符分隔，字形索引以占位字符表示
 // 返回: string 原文
 func (obj TextObject) Text() string {
+	obj.TextCode = textCodeOrigins(obj.TextCode, 0)
 	var text strings.Builder
 	for i, code := range obj.TextCode {
 		if obj.textCodeLineBreak(i) {
@@ -66,12 +67,33 @@ func (tc *TextCode) GetDeltaY() []float64 {
 // 入参: index 文本编码索引
 // 返回: bool 是否换行
 func (obj TextObject) textCodeLineBreak(index int) bool {
-	if index == 0 || obj.ReadDirection != 0 || obj.CharDirection != 0 {
+	if index == 0 || obj.ReadDirection != 0 || obj.CharDirection != 0 || obj.TextCode[index].Y == "" {
 		return false
 	}
 	code, previous := obj.TextCode[index], obj.TextCode[index-1]
+	for i := index - 2; i >= 0 && (previous.X == "" || previous.Y == ""); i-- {
+		if previous.X == "" {
+			previous.X = obj.TextCode[i].X
+		}
+		if previous.Y == "" {
+			previous.Y = obj.TextCode[i].Y
+		}
+	}
+	if previous.X == "" {
+		previous.X = "0"
+	}
+	if previous.Y == "" {
+		previous.Y = "0"
+	}
+	if code.X == "" {
+		code.X = previous.X
+	}
+	startX := obj.TextCode[0].X
+	if startX == "" {
+		startX = "0"
+	}
 	x, ex := strconv.ParseFloat(code.X, 64)
-	start, es := strconv.ParseFloat(obj.TextCode[0].X, 64)
+	start, es := strconv.ParseFloat(startX, 64)
 	y, ey := strconv.ParseFloat(code.Y, 64)
 	prev, ep := strconv.ParseFloat(previous.Y, 64)
 	if ex != nil || es != nil || ey != nil || ep != nil {

ofdgo_text_position.go

@@ -14,6 +14,8 @@
 
 package ofdgo
 
+import "slices"
+
 // 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
@@ -23,6 +25,35 @@ type TextPositioner struct {
 	index            int
 }
 
+// textCodeOrigins 按标准继承文本段原点，首段缺失坐标时以零横坐标和字体上升高度容错恢复
+// 入参: codes 文本段, ascent 对象坐标系下的字体上升高度
+// 返回: []TextCode 定位文本段，不修改原始数据
+func textCodeOrigins(codes []TextCode, ascent float64) []TextCode {
+	for i, code := range codes {
+		if code.X != "" && code.Y != "" {
+			continue
+		}
+		result := slices.Clone(codes)
+		var x, y string
+		if i > 0 {
+			x, y = codes[i-1].X, codes[i-1].Y
+		} else {
+			x, y = "0", ofdNumber(ascent)
+		}
+		for j := i; j < len(result); j++ {
+			if result[j].X == "" {
+				result[j].X = x
+			}
+			if result[j].Y == "" {
+				result[j].Y = y
+			}
+			x, y = result[j].X, result[j].Y
+		}
+		return result
+	}
+	return codes
+}
+
 // 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