feat(写入支持): 新增OFD文档创建与保存能力

README.md

@@ -1,5 +1,5 @@
 # OFDGo [![PkgGoDev](https://pkg.go.dev/badge/github.com/xiaoqidun/ofdgo)](https://pkg.go.dev/github.com/xiaoqidun/ofdgo)
-首个原生、全平台兼容的纯 Go 语言 OFD 渲染库
+首个原生、全平台兼容的纯 Go 语言 OFD 读写库
 
 
 # 在线体验
@@ -105,5 +105,49 @@ func main() {
 }
 ```
 
+# 创建文档
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/xiaoqidun/ofdgo"
+)
+
+func main() {
+	// 1. 创建文档
+	editor := ofdgo.NewEditor()
+	editor.Info.Title = "示例文档"
+	page, err := editor.AddPage(210, 297)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// 2. 添加文字
+	fontData, err := os.ReadFile("font.ttf")
+	if err != nil {
+		log.Fatal(err)
+	}
+	fontID, err := editor.AddFont(ofdgo.FontFile{Data: fontData}, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+	_, err = editor.AddText(page, ofdgo.Box{X: 20, Y: 20, W: 170, H: 15}, "你好，OFDGo！", fontID, 6)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// 3. 保存文档
+	ofdFile, err := os.Create("test.ofd")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer ofdFile.Close()
+	if _, err := editor.WriteTo(ofdFile); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
 # 授权协议
 本项目使用 [Apache License 2.0](https://github.com/xiaoqidun/ofdgo/blob/main/LICENSE) 授权协议

ofdgo.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package ofdgo 首个原生、全平台兼容的纯 Go 语言 OFD 渲染库
+// Package ofdgo 首个原生、全平台兼容的纯 Go 语言 OFD 读写库
 package ofdgo
 
 import (

ofdgo_editor.go

@@ -0,0 +1,580 @@
+// 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 (
+	"bytes"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/xml"
+	"fmt"
+	"image"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/tdewolff/font"
+)
+
+// Editor 新建OFD文档，长度单位为毫米，页面索引从0开始，实例需串行使用
+// Info可修改文档元数据，页面和资源通过方法添加，不修改已有OFD文件
+type Editor struct {
+	Info       DocInfo
+	pages      []PageContent
+	resources  []editorResource
+	fonts      map[string]*font.SFNT
+	images     map[string]bool
+	resourceID map[editorResourceKey]string
+	maxID      int
+}
+
+// editorResource 文档内嵌资源
+type editorResource struct {
+	name  string
+	data  []byte
+	font  *Font
+	image *MultiMedia
+}
+
+// editorResourceKey 资源内容和字体集合索引
+type editorResourceKey struct {
+	checksum [32]byte
+	index    int
+}
+
+// NewEditor 创建空白文档，保存前至少添加一页
+// 返回: *Editor 文档编辑器
+func NewEditor() *Editor {
+	var id [16]byte
+	rand.Read(id[:])
+	id[6] = id[6]&0x0f | 0x40
+	id[8] = id[8]&0x3f | 0x80
+	return &Editor{
+		Info: DocInfo{
+			DocID:        hex.EncodeToString(id[:]),
+			CreationDate: time.Now().Format("2006-01-02"),
+		},
+		fonts:      make(map[string]*font.SFNT),
+		images:     make(map[string]bool),
+		resourceID: make(map[editorResourceKey]string),
+	}
+}
+
+// AddPage 添加页面及默认正文图层
+// 入参: width 页面宽度, height 页面高度
+// 返回: int 页面索引, error 错误信息
+func (e *Editor) AddPage(width, height float64) (int, error) {
+	if !finite(width) || !finite(height) || width <= 0 || height <= 0 {
+		return 0, fmt.Errorf("page dimensions must be finite and positive")
+	}
+	e.pages = append(e.pages, PageContent{
+		ID:      e.nextID(),
+		Area:    PageArea{PhysicalBox: fmt.Sprintf("0 0 %s %s", ofdNumber(width), ofdNumber(height))},
+		Content: Content{Layer: []Layer{{ID: e.nextID(), Type: "Body"}}},
+	})
+	return len(e.pages) - 1, nil
+}
+
+// nextID 分配文档内唯一标识
+// 返回: string 对象标识
+func (e *Editor) nextID() string {
+	e.maxID++
+	return strconv.Itoa(e.maxID)
+}
+
+// AddFont 嵌入OpenType字体，集合字体按索引提取，重复资源复用标识
+// 入参: file 字体文件, index 集合内字体索引，单字体为0
+// 返回: string 字体资源标识, error 错误信息
+func (e *Editor) AddFont(file FontFile, index int) (string, error) {
+	if index < 0 {
+		return "", fmt.Errorf("font index must not be negative")
+	}
+	data, err := font.ToSFNT(file.Data)
+	if err != nil {
+		return "", err
+	}
+	key := editorResourceKey{checksum: sha256.Sum256(data), index: index}
+	if id, ok := e.resourceID[key]; ok {
+		return id, nil
+	}
+	if bytes.HasPrefix(data, []byte("ttcf")) {
+		data, err = extractCollectionFont(data, index)
+		if err != nil {
+			return "", err
+		}
+		index = 0
+	} else {
+		data = bytes.Clone(data)
+	}
+	sfnt, err := font.ParseSFNT(data, index)
+	if err != nil {
+		return "", err
+	}
+	name := editorFontName(sfnt, font.NamePostScript, font.NameFull, font.NameFontFamily)
+	if name == "" {
+		return "", fmt.Errorf("font has no name")
+	}
+	id := e.nextID()
+	extension := ".ttf"
+	if sfnt.IsCFF {
+		extension = ".otf"
+	}
+	resource := editorResource{
+		name: "Doc_0/Res/Font_" + id + extension,
+		data: data,
+		font: &Font{
+			ID: id, FontName: name,
+			FamilyName: editorFontName(sfnt, font.NamePreferredFamily, font.NameFontFamily),
+			Charset:    "unicode",
+			Bold:       sfnt.Head.MacStyle[0],
+			Italic:     sfnt.Head.MacStyle[1],
+			FixedWidth: sfnt.Post.IsFixedPitch != 0,
+		},
+	}
+	resource.font.FontFile = strings.TrimPrefix(resource.name, "Doc_0/Res/")
+	e.resources = append(e.resources, resource)
+	e.fonts[id] = sfnt
+	e.resourceID[key] = id
+	return id, nil
+}
+
+// editorFontName 获取字体中的名称
+// 入参: sfnt 字体, names 名称类型，按顺序查找
+// 返回: string 字体名称
+func editorFontName(sfnt *font.SFNT, names ...font.NameID) string {
+	for _, name := range names {
+		for _, record := range sfnt.Name.Get(name) {
+			if value := record.String(); value != "" {
+				return value
+			}
+		}
+	}
+	return ""
+}
+
+// AddImage 嵌入PNG或JPEG图片，保留原始编码，重复资源复用标识
+// 入参: data 图片数据
+// 返回: string 图片资源标识, error 错误信息
+func (e *Editor) AddImage(data []byte) (string, error) {
+	config, format, err := image.DecodeConfig(bytes.NewReader(data))
+	if err != nil {
+		return "", err
+	}
+	if (format != "png" && format != "jpeg") || config.Width <= 0 || config.Height <= 0 {
+		return "", fmt.Errorf("only PNG and JPEG images are supported")
+	}
+	key := editorResourceKey{checksum: sha256.Sum256(data), index: -1}
+	if id, ok := e.resourceID[key]; ok {
+		return id, nil
+	}
+	id := e.nextID()
+	extension := format
+	if extension == "jpeg" {
+		extension = "jpg"
+	}
+	name := "Image_" + id + "." + extension
+	e.resources = append(e.resources, editorResource{
+		name:  "Doc_0/Res/" + name,
+		data:  bytes.Clone(data),
+		image: &MultiMedia{ID: id, Type: "Image", Format: strings.ToUpper(format), MediaFile: name},
+	})
+	e.images[id] = true
+	e.resourceID[key] = id
+	return id, nil
+}
+
+// AddObject 按添加顺序放入正文图层，支持文字、路径和图片，自动分配对象ID
+// 首版支持基本颜色和直接资源引用，不支持动作、裁剪、渐变及复合图元
+// 入参: page 页面索引, object 对象内容，添加后不再引用调用方的可变数据
+// 返回: string 对象标识, error 错误信息
+func (e *Editor) AddObject(page int, object GraphicObject) (string, error) {
+	if page < 0 || page >= len(e.pages) {
+		return "", fmt.Errorf("page index %d out of range", page)
+	}
+	id := strconv.Itoa(e.maxID + 1)
+	var boundary, ctm, drawParam, join string
+	var alpha *int
+	var clips *Clips
+	var actions []Action
+	var fill, stroke *FillColor
+	switch object.Type {
+	case "TextObject":
+		obj := &object.TextObject
+		if err := e.prepareText(obj); err != nil {
+			return "", err
+		}
+		obj.ID = id
+		boundary, ctm, drawParam = obj.Boundary, obj.CTM, obj.DrawParam
+		join = obj.Join
+		alpha, clips, actions = obj.Alpha, obj.Clips, obj.Actions
+		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
+	case "PathObject":
+		obj := &object.PathObject
+		if err := creationPath(obj.AbbreviatedData); err != nil {
+			return "", err
+		}
+		if obj.Rule != "" && obj.Rule != "NonZero" && obj.Rule != "Even-Odd" {
+			return "", fmt.Errorf("invalid fill rule %q", obj.Rule)
+		}
+		if !finite(obj.LineWidth) || obj.LineWidth < 0 || !finite(obj.MiterLimit) || obj.MiterLimit < 0 {
+			return "", fmt.Errorf("invalid path stroke dimensions")
+		}
+		if obj.Cap != "" && obj.Cap != "Butt" && obj.Cap != "Round" && obj.Cap != "Square" {
+			return "", fmt.Errorf("invalid line cap %q", obj.Cap)
+		}
+		if obj.DashOffset != nil && !finite(*obj.DashOffset) {
+			return "", fmt.Errorf("invalid dash offset")
+		}
+		if obj.DashPattern != "" {
+			values, err := creationNumbers(obj.DashPattern, len(strings.Fields(obj.DashPattern)))
+			if err != nil {
+				return "", err
+			}
+			total := 0.0
+			for _, value := range values {
+				if value < 0 {
+					return "", fmt.Errorf("dash lengths must not be negative")
+				}
+				total += value
+			}
+			if total == 0 {
+				return "", fmt.Errorf("dash pattern must have a positive length")
+			}
+		}
+		obj.ID = id
+		boundary, ctm, drawParam = obj.Boundary, obj.CTM, obj.DrawParam
+		join = obj.Join
+		alpha, clips, actions = obj.Alpha, obj.Clips, obj.Actions
+		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
+	case "ImageObject":
+		obj := &object.ImageObject
+		if !e.images[obj.ResourceID] || (obj.ImageMask != "" && !e.images[obj.ImageMask]) {
+			return "", fmt.Errorf("image resource not found")
+		}
+		if obj.Border != nil {
+			return "", fmt.Errorf("image borders are not supported for creation")
+		}
+		obj.ID = id
+		boundary, ctm = obj.Boundary, obj.CTM
+		alpha, clips, actions = obj.Alpha, obj.Clips, obj.Actions
+	default:
+		return "", fmt.Errorf("unsupported object type %q", object.Type)
+	}
+	box, err := creationBox(boundary)
+	if err != nil {
+		return "", err
+	}
+	if ctm != "" {
+		if _, err := creationNumbers(ctm, 6); err != nil {
+			return "", fmt.Errorf("invalid CTM: %w", err)
+		}
+	} else if object.Type == "ImageObject" {
+		object.ImageObject.CTM = fmt.Sprintf("%s 0 0 %s 0 0", ofdNumber(box.W), ofdNumber(box.H))
+	}
+	if drawParam != "" || clips != nil || len(actions) != 0 {
+		return "", fmt.Errorf("draw parameter references, clips and actions are not supported for creation")
+	}
+	if alpha != nil && (*alpha < 0 || *alpha > 255) {
+		return "", fmt.Errorf("alpha must be between 0 and 255")
+	}
+	for _, color := range []*FillColor{fill, stroke} {
+		if err := creationColor(color); err != nil {
+			return "", err
+		}
+	}
+	if join != "" && join != "Miter" && join != "Round" && join != "Bevel" {
+		return "", fmt.Errorf("invalid line join %q", join)
+	}
+	data, err := objectXML(object)
+	if err != nil {
+		return "", err
+	}
+	object = GraphicObject{Type: object.Type}
+	var target any
+	switch object.Type {
+	case "TextObject":
+		target = &object.TextObject
+	case "PathObject":
+		target = &object.PathObject
+	case "ImageObject":
+		target = &object.ImageObject
+	}
+	if err := xml.Unmarshal(data, target); err != nil {
+		return "", err
+	}
+	e.maxID++
+	e.pages[page].Content.Layer[0].Objects = append(e.pages[page].Content.Layer[0].Objects, object)
+	return id, nil
+}
+
+// AddText 添加单行文字，使用嵌入字体的字宽定位，不进行段落排版和复杂文字塑形
+// 入参: page 页面索引, box 文字边界, value 原文, fontID 字体资源标识, size 字号
+// 返回: string 对象标识, error 错误信息
+func (e *Editor) AddText(page int, box Box, value, fontID string, size float64) (string, error) {
+	sfnt, ok := e.fonts[fontID]
+	if !ok {
+		return "", fmt.Errorf("font resource %q not found", fontID)
+	}
+	if !utf8.ValidString(value) || strings.ContainsAny(value, "\r\n\t") || value == "" {
+		return "", fmt.Errorf("text must be a nonempty UTF-8 line")
+	}
+	runes := []rune(value)
+	deltas := make([]string, 0, len(runes)-1)
+	for i, char := range runes {
+		glyph := sfnt.GlyphIndex(char)
+		if glyph == 0 {
+			return "", fmt.Errorf("font does not contain U+%04X", char)
+		}
+		if i+1 < len(runes) {
+			deltas = append(deltas, ofdNumber(float64(sfnt.GlyphAdvance(glyph))*size/float64(sfnt.UnitsPerEm())))
+		}
+	}
+	ascender, _, _ := sfnt.VerticalMetrics()
+	return e.AddObject(page, GraphicObject{Type: "TextObject", TextObject: TextObject{
+		Boundary: fmt.Sprintf("%s %s %s %s", ofdNumber(box.X), ofdNumber(box.Y), ofdNumber(box.W), ofdNumber(box.H)),
+		Font:     fontID, Size: size,
+		TextCode: []TextCode{{X: "0", Y: ofdNumber(float64(ascender) * size / float64(sfnt.UnitsPerEm())), DeltaX: strings.Join(deltas, " "), Value: escapeOFDText(value)}},
+	}})
+}
+
+// prepareText 校验并补全标准文字定位，避免依赖阅读器的缺省字距补偿
+// 入参: obj 文字对象
+// 返回: error 错误信息
+func (e *Editor) prepareText(obj *TextObject) error {
+	if e.fonts[obj.Font] == nil || !finite(obj.Size) || obj.Size <= 0 {
+		return fmt.Errorf("text requires an embedded font and a positive finite size")
+	}
+	if len(obj.TextCode) == 0 {
+		return fmt.Errorf("text codes are empty")
+	}
+	if obj.VScale != 0 || obj.Decoration != "" || len(obj.CGTransform) != 0 {
+		return fmt.Errorf("text extensions and glyph transforms are not supported for creation")
+	}
+	if !finite(obj.HScale) || obj.HScale < 0 || !finite(obj.LineWidth) || obj.LineWidth < 0 || !finite(obj.MiterLimit) || obj.MiterLimit < 0 {
+		return fmt.Errorf("invalid text dimensions")
+	}
+	if obj.Weight < 0 || obj.Weight > 900 || obj.Weight%100 != 0 {
+		return fmt.Errorf("invalid text weight")
+	}
+	for _, direction := range []int{obj.ReadDirection, obj.CharDirection} {
+		if direction != 0 && direction != 90 && direction != 180 && direction != 270 {
+			return fmt.Errorf("invalid text direction %d", direction)
+		}
+	}
+	obj.TextCode = append([]TextCode(nil), obj.TextCode...)
+	x, y := "", ""
+	for i := range obj.TextCode {
+		code := &obj.TextCode[i]
+		if code.Index != "" || !utf8.ValidString(code.Value) {
+			return fmt.Errorf("text requires Unicode character data")
+		}
+		if code.X != "" {
+			x = code.X
+		}
+		if code.Y != "" {
+			y = code.Y
+		}
+		for _, coordinate := range []string{x, y} {
+			if _, err := creationNumbers(coordinate, 1); err != nil {
+				return fmt.Errorf("invalid text origin: %w", err)
+			}
+		}
+		code.X, code.Y = x, y
+		runes := textCodeRunes(code.Value)
+		if len(runes) == 0 {
+			return fmt.Errorf("text code is empty")
+		}
+		for _, char := range runes {
+			if e.fonts[obj.Font].GlyphIndex(char) == 0 {
+				return fmt.Errorf("font does not contain U+%04X", char)
+			}
+		}
+		for _, delta := range []string{code.DeltaX, code.DeltaY} {
+			if delta != "" {
+				if err := creationDeltas(delta, len(runes)-1); err != nil {
+					return fmt.Errorf("invalid text delta: %w", err)
+				}
+			}
+		}
+		if len(runes) > 1 && code.DeltaX == "" && code.DeltaY == "" {
+			code.DeltaX = strings.TrimSpace(strings.Repeat("0 ", len(runes)-1))
+		}
+		code.Value = escapeOFDText(string(runes))
+	}
+	return nil
+}
+
+// creationDeltas 校验文字位移数组及g重复编码
+// 入参: value 位移数组, count 所需位移数量
+// 返回: error 错误信息
+func creationDeltas(value string, count int) error {
+	fields := strings.Fields(value)
+	numbers := 0
+	for i := 0; i < len(fields); i++ {
+		repeat := 1
+		if fields[i] == "g" {
+			if i+2 >= len(fields) {
+				return fmt.Errorf("incomplete delta repetition")
+			}
+			var err error
+			repeat, err = strconv.Atoi(fields[i+1])
+			if err != nil || repeat <= 0 {
+				return fmt.Errorf("invalid delta repetition")
+			}
+			i += 2
+		}
+		if _, err := creationNumbers(fields[i], 1); err != nil {
+			return err
+		}
+		if repeat > count-numbers {
+			return fmt.Errorf("too many text deltas")
+		}
+		numbers += repeat
+	}
+	if numbers != count {
+		return fmt.Errorf("expected %d text deltas", count)
+	}
+	return nil
+}
+
+// creationPath 校验紧缩路径的命令及有限数值参数
+// 入参: value 路径数据
+// 返回: error 错误信息
+func creationPath(value string) error {
+	tokens := strings.Fields(value)
+	if len(tokens) == 0 || (tokens[0] != "M" && tokens[0] != "S") {
+		return fmt.Errorf("path must start with M or S")
+	}
+	for i := 0; i < len(tokens); {
+		command := tokens[i]
+		i++
+		count := 0
+		switch command {
+		case "M", "S", "L":
+			count = 2
+		case "Q":
+			count = 4
+		case "B":
+			count = 6
+		case "A":
+			count = 7
+		case "C":
+		default:
+			return fmt.Errorf("invalid path command %q", command)
+		}
+		if len(tokens)-i < count {
+			return fmt.Errorf("missing arguments for path command %s", command)
+		}
+		values, err := creationNumbers(strings.Join(tokens[i:i+count], " "), count)
+		if err != nil {
+			return err
+		}
+		if command == "A" && (values[0] < 0 || values[1] < 0 || (values[3] != 0 && values[3] != 1) || (values[4] != 0 && values[4] != 1)) {
+			return fmt.Errorf("invalid arc radii or flags")
+		}
+		i += count
+	}
+	return nil
+}
+
+// creationNumbers 解析创建接口的有限十进制数值序列
+// 入参: value 数值序列, count 数值数量
+// 返回: []float64 数值, error 错误信息
+func creationNumbers(value string, count int) ([]float64, error) {
+	fields := strings.Fields(value)
+	if len(fields) != count {
+		return nil, fmt.Errorf("expected %d numbers", count)
+	}
+	values := make([]float64, count)
+	for i, field := range fields {
+		number, err := strconv.ParseFloat(field, 64)
+		if err != nil || !finite(number) || strings.ContainsAny(field, "xX_") {
+			return nil, fmt.Errorf("invalid number %q", field)
+		}
+		values[i] = number
+	}
+	return values, nil
+}
+
+// creationBox 校验对象边界
+// 入参: value 边界描述
+// 返回: Box 矩形, error 错误信息
+func creationBox(value string) (Box, error) {
+	values, err := creationNumbers(value, 4)
+	if err != nil {
+		return Box{}, err
+	}
+	if values[2] <= 0 || values[3] <= 0 {
+		return Box{}, fmt.Errorf("boundary dimensions must be positive")
+	}
+	return Box{X: values[0], Y: values[1], W: values[2], H: values[3]}, nil
+}
+
+// creationColor 校验默认RGB颜色空间中的基本颜色
+// 入参: color 颜色
+// 返回: error 错误信息
+func creationColor(color *FillColor) error {
+	if color == nil {
+		return nil
+	}
+	if color.ColorSpace != "" || color.Index != nil || color.Pattern != nil || color.AxialShd != nil || color.RadialShd != nil || color.unsupported {
+		return fmt.Errorf("only direct RGB colors are supported for creation")
+	}
+	values, err := creationNumbers(color.Value, 3)
+	if err != nil {
+		return err
+	}
+	for _, value := range values {
+		if value < 0 || value > 255 || math.Trunc(value) != value {
+			return fmt.Errorf("RGB channels must be integers between 0 and 255")
+		}
+	}
+	if color.Alpha != nil && (*color.Alpha < 0 || *color.Alpha > 255) {
+		return fmt.Errorf("color alpha must be between 0 and 255")
+	}
+	return nil
+}
+
+// finite 判断数值是否有限
+// 入参: value 数值
+// 返回: bool 是否有限
+func finite(value float64) bool {
+	return !math.IsNaN(value) && !math.IsInf(value, 0)
+}
+
+// ofdNumber 格式化OFD数值
+// 入参: value 数值
+// 返回: string 数值文本
+func ofdNumber(value float64) string {
+	return strconv.FormatFloat(value, 'f', -1, 64)
+}
+
+// escapeOFDText 转义控制字符、反斜线和XML不允许的字符
+// 入参: value 原文
+// 返回: string OFD文字编码
+func escapeOFDText(value string) string {
+	var text strings.Builder
+	for _, char := range value {
+		if char < ' ' || char == '\\' || char == '\ufffe' || char == '\uffff' {
+			fmt.Fprintf(&text, "\\%04X", char)
+		} else {
+			text.WriteRune(char)
+		}
+	}
+	return text.String()
+}

ofdgo_font_util.go

@@ -17,9 +17,57 @@ package ofdgo
 import (
 	"bytes"
 	"encoding/binary"
+	"fmt"
 	"sort"
 )
 
+// extractCollectionFont 提取集合中的单个OpenType字体，保留表内容并重新计算校验和
+// 入参: data 集合数据, index 字体索引
+// 返回: []byte 单字体数据, error 错误信息
+func extractCollectionFont(data []byte, index int) ([]byte, error) {
+	if len(data) < 12 || string(data[:4]) != "ttcf" {
+		return nil, fmt.Errorf("invalid font collection header")
+	}
+	version := binary.BigEndian.Uint32(data[4:])
+	count := uint64(binary.BigEndian.Uint32(data[8:]))
+	if (version != 0x00010000 && version != 0x00020000) || count > uint64(len(data)-12)/4 || index < 0 || uint64(index) >= count {
+		return nil, fmt.Errorf("invalid font collection index or version")
+	}
+	offset := uint64(binary.BigEndian.Uint32(data[12+index*4:]))
+	if offset > uint64(len(data)-12) {
+		return nil, fmt.Errorf("invalid font offset")
+	}
+	header := data[offset : offset+12]
+	if string(header[:4]) != "\x00\x01\x00\x00" && string(header[:4]) != "OTTO" && string(header[:4]) != "true" {
+		return nil, fmt.Errorf("invalid OpenType header")
+	}
+	tableCount := uint64(binary.BigEndian.Uint16(header[4:]))
+	offset += 12
+	if tableCount == 0 || tableCount > (uint64(len(data))-offset)/16 {
+		return nil, fmt.Errorf("invalid font table directory")
+	}
+	tables := make(map[string][]byte, tableCount)
+	for i := uint64(0); i < tableCount; i++ {
+		entry := data[offset+i*16 : offset+(i+1)*16]
+		tag := string(entry[:4])
+		start := uint64(binary.BigEndian.Uint32(entry[8:]))
+		length := uint64(binary.BigEndian.Uint32(entry[12:]))
+		if start > uint64(len(data)) || length > uint64(len(data))-start {
+			return nil, fmt.Errorf("invalid %s font table range", tag)
+		}
+		if _, exists := tables[tag]; exists {
+			return nil, fmt.Errorf("duplicate %s font table", tag)
+		}
+		tables[tag] = data[start : start+length]
+	}
+	if len(tables["head"]) < 12 {
+		return nil, fmt.Errorf("invalid head font table")
+	}
+	tables["head"] = bytes.Clone(tables["head"])
+	clear(tables["head"][8:12])
+	return serializeOTF(tables)
+}
+
 // packedGlyphRune 获取包装字体字符
 // 入参: gid 字形ID
 // 返回: rune 包装字体字符

ofdgo_reader.go

@@ -46,6 +46,7 @@ type Reader struct {
 	Annots                    map[string][]Annotation
 	fileIndex                 map[string]*zip.File
 	fileIndexFold             map[string]*zip.File
+	files                     map[string][]byte
 }
 
 // Close 关闭阅读器
@@ -62,12 +63,14 @@ func (r *Reader) Close() error {
 func (r *Reader) initRoot() error {
 	r.fileIndex = make(map[string]*zip.File)
 	r.fileIndexFold = make(map[string]*zip.File)
-	for _, f := range r.Zip.File {
-		name := cleanPackagePath(f.Name)
-		r.fileIndex[name] = f
-		fold := strings.ToLower(name)
-		if _, ok := r.fileIndexFold[fold]; !ok {
-			r.fileIndexFold[fold] = f
+	if r.Zip != nil {
+		for _, f := range r.Zip.File {
+			name := cleanPackagePath(f.Name)
+			r.fileIndex[name] = f
+			fold := strings.ToLower(name)
+			if _, ok := r.fileIndexFold[fold]; !ok {
+				r.fileIndexFold[fold] = f
+			}
 		}
 	}
 	data, err := r.readFile("OFD.xml")
@@ -90,22 +93,28 @@ func (r *Reader) initRoot() error {
 	return nil
 }
 
-// readFile 读取压缩包内的文件
+// readFile 读取文档内的文件
 // 入参: name 文件名
 // 返回: []byte 文件内容, error 错误信息
 func (r *Reader) readFile(name string) ([]byte, error) {
 	name = cleanPackagePath(name)
+	if data, ok := r.files[name]; ok {
+		return bytes.Clone(data), nil
+	}
 	if f, ok := r.packageFile(name); ok {
 		return readZipFile(f)
 	}
 	return nil, fmt.Errorf("file not found: %s", name)
 }
 
-// openFile 打开压缩包内的文件流
+// openFile 打开文档内的文件流
 // 入参: name 文件名
 // 返回: io.ReadCloser 文件流, error 错误信息
 func (r *Reader) openFile(name string) (io.ReadCloser, error) {
 	name = cleanPackagePath(name)
+	if data, ok := r.files[name]; ok {
+		return io.NopCloser(bytes.NewReader(data)), nil
+	}
 	if f, ok := r.packageFile(name); ok {
 		return f.Open()
 	}

ofdgo_text.go

@@ -18,6 +18,7 @@ import (
 	"math"
 	"strconv"
 	"strings"
+	"unicode/utf16"
 
 	"github.com/tdewolff/canvas"
 	canvastext "github.com/tdewolff/canvas/text"
@@ -322,7 +323,31 @@ func textCodeRunes(value string) []rune {
 	if strings.ContainsAny(value, "\r\n") {
 		value = strings.TrimSpace(value)
 	}
-	return []rune(value)
+	runes := []rune(value)
+	if !strings.Contains(value, "\\") {
+		return runes
+	}
+	written := 0
+	for i := 0; i < len(runes); i++ {
+		char := runes[i]
+		if char == '\\' && i+4 < len(runes) {
+			if code, err := strconv.ParseUint(string(runes[i+1:i+5]), 16, 16); err == nil {
+				decoded := rune(code)
+				if !utf16.IsSurrogate(decoded) {
+					char = decoded
+					i += 4
+				} else if decoded >= 0xd800 && decoded <= 0xdbff && i+9 < len(runes) && runes[i+5] == '\\' {
+					if low, err := strconv.ParseUint(string(runes[i+6:i+10]), 16, 16); err == nil && low >= 0xdc00 && low <= 0xdfff {
+						char = utf16.DecodeRune(decoded, rune(low))
+						i += 9
+					}
+				}
+			}
+		}
+		runes[written] = char
+		written++
+	}
+	return runes[:written]
 }
 
 // GetDeltaX 获取X轴偏移量数组

ofdgo_writer.go

@@ -0,0 +1,485 @@
+// 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 (
+	"archive/zip"
+	"bytes"
+	"encoding/hex"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"strconv"
+	"time"
+)
+
+const ofdNamespace = "http://www.ofdspec.org/2016"
+
+// WriteTo 逐个条目写出OFD，不关闭调用方输出流，出错时应丢弃本次输出
+// 入参: writer 输出流
+// 返回: int64 已写入字节数, error 错误信息
+func (e *Editor) WriteTo(writer io.Writer) (int64, error) {
+	if err := e.validate(); err != nil {
+		return 0, err
+	}
+	output := &ofdCountingWriter{writer: writer}
+	archive := zip.NewWriter(output)
+	err := e.writeParts(func(name string, data []byte, compressed bool) error {
+		method := uint16(zip.Deflate)
+		if compressed {
+			method = zip.Store
+		}
+		entry, err := archive.CreateHeader(&zip.FileHeader{Name: name, Method: method})
+		if err != nil {
+			return err
+		}
+		_, err = entry.Write(data)
+		return err
+	})
+	if err == nil {
+		err = archive.Close()
+	}
+	return output.count, err
+}
+
+// Reader 获取当前文档的独立内存快照，不进行ZIP压缩，后续修改不影响已有快照
+// 返回的Reader可用于现有渲染、搜索和导出接口，二进制资源内部共享只读数据
+// 返回: *Reader 阅读器, error 错误信息
+func (e *Editor) Reader() (*Reader, error) {
+	if err := e.validate(); err != nil {
+		return nil, err
+	}
+	r := &Reader{files: make(map[string][]byte)}
+	if err := e.writeParts(func(name string, data []byte, _ bool) error {
+		r.files[name] = data
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	if err := r.initRoot(); err != nil {
+		return nil, err
+	}
+	if _, err := r.Doc(); err != nil {
+		return nil, err
+	}
+	return r, nil
+}
+
+// validate 校验文档保存条件
+// 返回: error 错误信息
+func (e *Editor) validate() error {
+	if len(e.pages) == 0 {
+		return fmt.Errorf("document must contain at least one page")
+	}
+	if data, err := hex.DecodeString(e.Info.DocID); err != nil || len(data) != 16 {
+		return fmt.Errorf("DocID must contain 32 hexadecimal characters")
+	}
+	for _, date := range []string{e.Info.CreationDate, e.Info.ModDate} {
+		if date != "" {
+			if _, err := time.Parse("2006-01-02", date); err != nil {
+				return fmt.Errorf("invalid document date: %w", err)
+			}
+		}
+	}
+	return nil
+}
+
+// writeParts 生成根节点、文档、资源索引、页面及二进制资源
+// 入参: write 条目写入方法
+// 返回: error 错误信息
+func (e *Editor) writeParts(write func(string, []byte, bool) error) error {
+	writeXML := func(name string, encode func(*ofdXML)) error {
+		var data bytes.Buffer
+		x := newOFDXML(&data)
+		encode(x)
+		if err := x.finish(); err != nil {
+			return err
+		}
+		return write(name, data.Bytes(), false)
+	}
+	if err := writeXML("OFD.xml", func(x *ofdXML) {
+		x.root("OFD", ofdAttrs{{Name: xml.Name{Local: "Version"}, Value: "1.0"}, {Name: xml.Name{Local: "DocType"}, Value: "OFD"}})
+		x.start("DocBody", nil)
+		x.start("DocInfo", nil)
+		for _, field := range [][2]string{
+			{"DocID", e.Info.DocID}, {"Title", e.Info.Title}, {"Author", e.Info.Author},
+			{"Subject", e.Info.Subject}, {"Abstract", e.Info.Abstract},
+			{"CreationDate", e.Info.CreationDate}, {"ModDate", e.Info.ModDate},
+			{"Creator", "xiaoqidun/ofdgo"},
+		} {
+			if field[1] != "" {
+				x.text(field[0], field[1])
+			}
+		}
+		if e.Info.CustomDatas != nil && len(e.Info.CustomDatas.CustomData) != 0 {
+			x.start("CustomDatas", nil)
+			for _, item := range e.Info.CustomDatas.CustomData {
+				attrs := ofdAttrs{{Name: xml.Name{Local: "Name"}, Value: item.Name}}
+				x.start("CustomData", attrs)
+				x.token(xml.CharData(item.Value))
+				x.end("CustomData")
+			}
+			x.end("CustomDatas")
+		}
+		x.end("DocInfo")
+		x.text("DocRoot", "Doc_0/Document.xml")
+		x.end("DocBody")
+		x.end("OFD")
+	}); err != nil {
+		return err
+	}
+	if err := writeXML("Doc_0/Document.xml", func(x *ofdXML) {
+		x.root("Document", nil)
+		x.start("CommonData", nil)
+		x.text("MaxUnitID", strconv.Itoa(e.maxID))
+		x.start("PageArea", nil)
+		x.text("PhysicalBox", e.pages[0].Area.PhysicalBox)
+		x.end("PageArea")
+		if len(e.resources) != 0 {
+			x.text("DocumentRes", "DocumentRes.xml")
+		}
+		x.end("CommonData")
+		x.start("Pages", nil)
+		for i, page := range e.pages {
+			var attrs ofdAttrs
+			attrs.add("ID", page.ID)
+			attrs.add("BaseLoc", fmt.Sprintf("Pages/%d/Content.xml", i+1))
+			x.start("Page", attrs)
+			x.end("Page")
+		}
+		x.end("Pages")
+		x.end("Document")
+	}); err != nil {
+		return err
+	}
+	if len(e.resources) != 0 {
+		if err := writeXML("Doc_0/DocumentRes.xml", e.writeResources); err != nil {
+			return err
+		}
+	}
+	for i, page := range e.pages {
+		if err := writeXML(fmt.Sprintf("Doc_0/Pages/%d/Content.xml", i+1), func(x *ofdXML) {
+			x.root("Page", nil)
+			x.start("Area", nil)
+			x.text("PhysicalBox", page.Area.PhysicalBox)
+			x.end("Area")
+			x.start("Content", nil)
+			for _, layer := range page.Content.Layer {
+				var attrs ofdAttrs
+				attrs.add("ID", layer.ID)
+				attrs.add("Type", layer.Type)
+				x.start("Layer", attrs)
+				for _, object := range layer.Objects {
+					x.object(object, false)
+				}
+				x.end("Layer")
+			}
+			x.end("Content")
+			x.end("Page")
+		}); err != nil {
+			return err
+		}
+	}
+	for _, resource := range e.resources {
+		if err := write(resource.name, resource.data, resource.image != nil); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// writeResources 写出文档资源索引
+// 入参: x XML编码器
+func (e *Editor) writeResources(x *ofdXML) {
+	x.root("Res", ofdAttrs{{Name: xml.Name{Local: "BaseLoc"}, Value: "Res"}})
+	if len(e.fonts) != 0 {
+		x.start("Fonts", nil)
+		for _, resource := range e.resources {
+			if resource.font == nil {
+				continue
+			}
+			font := resource.font
+			var attrs ofdAttrs
+			attrs.add("ID", font.ID)
+			attrs.add("FontName", font.FontName)
+			attrs.add("FamilyName", font.FamilyName)
+			attrs.add("Charset", font.Charset)
+			if font.Bold {
+				attrs.add("Bold", "true")
+			}
+			if font.Italic {
+				attrs.add("Italic", "true")
+			}
+			if font.FixedWidth {
+				attrs.add("FixedWidth", "true")
+			}
+			x.start("Font", attrs)
+			x.text("FontFile", font.FontFile)
+			x.end("Font")
+		}
+		x.end("Fonts")
+	}
+	if len(e.images) != 0 {
+		x.start("MultiMedias", nil)
+		for _, resource := range e.resources {
+			if resource.image == nil {
+				continue
+			}
+			image := resource.image
+			var attrs ofdAttrs
+			attrs.add("ID", image.ID)
+			attrs.add("Type", image.Type)
+			attrs.add("Format", image.Format)
+			x.start("MultiMedia", attrs)
+			x.text("MediaFile", image.MediaFile)
+			x.end("MultiMedia")
+		}
+		x.end("MultiMedias")
+	}
+	x.end("Res")
+}
+
+// ofdCountingWriter 记录实际输出字节数
+type ofdCountingWriter struct {
+	writer io.Writer
+	count  int64
+}
+
+// Write 写入并累计字节数
+// 入参: data 数据
+// 返回: int 字节数, error 错误信息
+func (w *ofdCountingWriter) Write(data []byte) (int, error) {
+	n, err := w.writer.Write(data)
+	w.count += int64(n)
+	if err == nil && n != len(data) {
+		err = io.ErrShortWrite
+	}
+	return n, err
+}
+
+// ofdXML 使用标准ofd命名空间写出XML
+type ofdXML struct {
+	encoder *xml.Encoder
+	err     error
+}
+
+// newOFDXML 创建XML编码器
+// 入参: writer 输出流
+// 返回: *ofdXML 编码器
+func newOFDXML(writer io.Writer) *ofdXML {
+	_, err := io.WriteString(writer, xml.Header)
+	return &ofdXML{encoder: xml.NewEncoder(writer), err: err}
+}
+
+// token 写入XML标记并保留首个错误
+// 入参: token XML标记
+func (x *ofdXML) token(token xml.Token) {
+	if x.err == nil {
+		x.err = x.encoder.EncodeToken(token)
+	}
+}
+
+// root 写入声明命名空间的根节点
+// 入参: name 节点名, attrs 属性
+func (x *ofdXML) root(name string, attrs ofdAttrs) {
+	attrs.add("xmlns:ofd", ofdNamespace)
+	x.start(name, attrs)
+}
+
+// start 写入节点起始标记
+// 入参: name 节点名, attrs 属性
+func (x *ofdXML) start(name string, attrs ofdAttrs) {
+	x.token(xml.StartElement{Name: xml.Name{Local: "ofd:" + name}, Attr: attrs})
+}
+
+// end 写入节点结束标记
+// 入参: name 节点名
+func (x *ofdXML) end(name string) {
+	x.token(xml.EndElement{Name: xml.Name{Local: "ofd:" + name}})
+}
+
+// text 写入文本节点
+// 入参: name 节点名, value 文本
+func (x *ofdXML) text(name, value string) {
+	x.start(name, nil)
+	x.token(xml.CharData(value))
+	x.end(name)
+}
+
+// finish 完成XML输出
+// 返回: error 错误信息
+func (x *ofdXML) finish() error {
+	if x.err != nil {
+		return x.err
+	}
+	return x.encoder.Close()
+}
+
+// ofdAttrs OFD节点属性
+type ofdAttrs []xml.Attr
+
+// add 添加非空属性
+// 入参: name 属性名, value 属性值
+func (a *ofdAttrs) add(name, value string) {
+	if value != "" {
+		*a = append(*a, xml.Attr{Name: xml.Name{Local: name}, Value: value})
+	}
+}
+
+// number 添加非零数值属性
+// 入参: name 属性名, value 数值
+func (a *ofdAttrs) number(name string, value float64) {
+	if value != 0 {
+		a.add(name, ofdNumber(value))
+	}
+}
+
+// flag 添加显式布尔属性
+// 入参: name 属性名, value 布尔值
+func (a *ofdAttrs) flag(name string, value *bool) {
+	if value != nil {
+		a.add(name, strconv.FormatBool(*value))
+	}
+}
+
+// alpha 添加显式透明度
+// 入参: value 透明度
+func (a *ofdAttrs) alpha(value *int) {
+	if value != nil {
+		a.add("Alpha", strconv.Itoa(*value))
+	}
+}
+
+// objectXML 编码单个对象，用于隔离调用方数据并统一读写语义
+// 入参: object 图形对象
+// 返回: []byte XML数据, error 错误信息
+func objectXML(object GraphicObject) ([]byte, error) {
+	var data bytes.Buffer
+	x := newOFDXML(&data)
+	x.object(object, true)
+	if err := x.finish(); err != nil {
+		return nil, err
+	}
+	return data.Bytes(), nil
+}
+
+// object 按OFD规定顺序写出基本对象
+// 入参: object 图形对象, root 是否为根节点
+func (x *ofdXML) object(object GraphicObject, root bool) {
+	var attrs ofdAttrs
+	var fill, stroke *FillColor
+	if root {
+		attrs.add("xmlns:ofd", ofdNamespace)
+	}
+	switch object.Type {
+	case "TextObject":
+		obj := object.TextObject
+		attrs.add("ID", obj.ID)
+		attrs.add("Boundary", obj.Boundary)
+		attrs.add("CTM", obj.CTM)
+		attrs.add("Font", obj.Font)
+		attrs.number("Size", obj.Size)
+		attrs.number("HScale", obj.HScale)
+		attrs.number("Weight", float64(obj.Weight))
+		attrs.number("ReadDirection", float64(obj.ReadDirection))
+		attrs.number("CharDirection", float64(obj.CharDirection))
+		attrs.number("LineWidth", obj.LineWidth)
+		attrs.number("MiterLimit", obj.MiterLimit)
+		attrs.add("Join", obj.Join)
+		if obj.Italic {
+			attrs.add("Italic", "true")
+		}
+		attrs.flag("Visible", obj.Visible)
+		attrs.flag("Stroke", obj.Stroke)
+		attrs.flag("Fill", obj.Fill)
+		attrs.alpha(obj.Alpha)
+		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
+	case "PathObject":
+		obj := object.PathObject
+		attrs.add("ID", obj.ID)
+		attrs.add("Boundary", obj.Boundary)
+		attrs.add("CTM", obj.CTM)
+		attrs.number("LineWidth", obj.LineWidth)
+		attrs.number("MiterLimit", obj.MiterLimit)
+		attrs.add("Join", obj.Join)
+		attrs.add("Cap", obj.Cap)
+		attrs.add("Rule", obj.Rule)
+		attrs.add("DashPattern", obj.DashPattern)
+		if obj.DashOffset != nil {
+			attrs.add("DashOffset", ofdNumber(*obj.DashOffset))
+		}
+		attrs.flag("Visible", obj.Visible)
+		attrs.flag("Stroke", obj.Stroke)
+		attrs.flag("Fill", obj.Fill)
+		attrs.alpha(obj.Alpha)
+		fill, stroke = obj.FillColor, (*FillColor)(obj.StrokeColor)
+	case "ImageObject":
+		obj := object.ImageObject
+		attrs.add("ID", obj.ID)
+		attrs.add("Boundary", obj.Boundary)
+		attrs.add("CTM", obj.CTM)
+		attrs.add("ResourceID", obj.ResourceID)
+		attrs.add("ImageMask", obj.ImageMask)
+		attrs.flag("Visible", obj.Visible)
+		attrs.alpha(obj.Alpha)
+	}
+	x.start(object.Type, attrs)
+	if object.Type == "PathObject" {
+		x.color("StrokeColor", stroke)
+		x.color("FillColor", fill)
+		x.text("AbbreviatedData", object.PathObject.AbbreviatedData)
+	} else if object.Type == "TextObject" {
+		x.color("FillColor", fill)
+		x.color("StrokeColor", stroke)
+		for _, code := range object.TextObject.TextCode {
+			var attrs ofdAttrs
+			attrs.add("X", code.X)
+			attrs.add("Y", code.Y)
+			attrs.add("DeltaX", code.DeltaX)
+			attrs.add("DeltaY", code.DeltaY)
+			x.textCode(code.Value, attrs)
+		}
+	}
+	x.end(object.Type)
+}
+
+// textCode 使用XML字符引用转义空格，避免依赖阅读器保留原始空白
+// 入参: value OFD文字内容, attrs 文字定位属性
+func (x *ofdXML) textCode(value string, attrs ofdAttrs) {
+	if x.err != nil {
+		return
+	}
+	var escaped bytes.Buffer
+	if x.err = xml.EscapeText(&escaped, []byte(value)); x.err != nil {
+		return
+	}
+	content := struct {
+		Text []byte `xml:",innerxml"`
+	}{Text: bytes.ReplaceAll(escaped.Bytes(), []byte(" "), []byte(" "))}
+	x.err = x.encoder.EncodeElement(content, xml.StartElement{Name: xml.Name{Local: "ofd:TextCode"}, Attr: attrs})
+}
+
+// color 写出基本颜色
+// 入参: name 节点名, color 颜色
+func (x *ofdXML) color(name string, color *FillColor) {
+	if color == nil {
+		return
+	}
+	var attrs ofdAttrs
+	attrs.add("Value", color.Value)
+	attrs.alpha(color.Alpha)
+	x.start(name, attrs)
+	x.end(name)
+}