feat(文件拆分): 拆分PDF格式适配模块

internal/base/threed/u3d.go

@@ -12,7 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package threed 提供U3D模型解码、场景求值及软件绘制能力
 package threed
 
 import (

internal/codec/pdf/clip.go

@@ -0,0 +1,67 @@
+// 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 pdf
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/binary"
+	"math"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// ClipPathKey 按路径完整内容与变换生成键，不依赖可变切片的地址
+// 入参: ctx 取消上下文, path 裁剪路径, matrix 页面变换
+// 返回: [32]byte 内容摘要, error 取消错误
+func ClipPathKey(ctx context.Context, path pdfgo.Path, matrix pdfgo.Matrix) ([32]byte, error) {
+	hash := sha256.New()
+	var value [16]byte
+	for _, number := range matrix {
+		binary.LittleEndian.PutUint64(value[:8], math.Float64bits(number))
+		hash.Write(value[:8])
+	}
+	binary.LittleEndian.PutUint64(value[:8], uint64(len(path.Segments)))
+	value[8] = 0
+	if path.EvenOdd {
+		value[8] = 1
+	}
+	hash.Write(value[:9])
+	for _, segment := range path.Segments {
+		if err := ctx.Err(); err != nil {
+			return [32]byte{}, err
+		}
+		binary.LittleEndian.PutUint64(value[:8], uint64(len(segment.Operator)))
+		binary.LittleEndian.PutUint64(value[8:], uint64(len(segment.Points)))
+		hash.Write(value[:])
+		hash.Write([]byte(segment.Operator))
+		for index, point := range segment.Points {
+			if index&255 == 0 {
+				if err := ctx.Err(); err != nil {
+					return [32]byte{}, err
+				}
+			}
+			binary.LittleEndian.PutUint64(value[:8], math.Float64bits(point.X))
+			binary.LittleEndian.PutUint64(value[8:], math.Float64bits(point.Y))
+			hash.Write(value[:])
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		return [32]byte{}, err
+	}
+	var key [32]byte
+	hash.Sum(key[:0])
+	return key, nil
+}

internal/codec/pdf/color.go

@@ -0,0 +1,37 @@
+// 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 pdf
+
+import (
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// OutputColor 将合成结果映射到OFD输出，与保留的设备四色对象使用相同显示换算
+// 入参: space 合成空间, values 非预乘分量
+// 返回: [3]float64 显示颜色, error 校准颜色转换错误
+func OutputColor(space *pdfgo.ColorSpace, values [4]float64) ([3]float64, error) {
+	if space.Model == "DeviceCMYK" && !space.Calibrated() {
+		black := 1 - values[3]
+		return [3]float64{(1 - values[0]) * black, (1 - values[1]) * black, (1 - values[2]) * black}, nil
+	}
+	return space.RGB(values[:space.Components()], "RelativeColorimetric")
+}
+
+// NormalBlend 判断混合模式是否为普通覆盖
+// 入参: mode 混合模式
+// 返回: bool 是否普通覆盖
+func NormalBlend(mode pdfgo.Name) bool {
+	return mode == "" || mode == "Normal" || mode == "Compatible"
+}

internal/codec/pdf/export.go

@@ -0,0 +1,195 @@
+// 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 pdf
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"image"
+	"io"
+
+	baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// TextPage 保存后端文字对象数量及待替换区段
+type TextPage struct {
+	Count        int
+	Replacements []pdfgo.TextReplacement
+}
+
+// WriteOptions 保存PDF最终写出所需的像素、文字和导航修正
+// Images逐页记录绘制图像，nil图像表示不替换；Links保留全部链接位置，包括矩形区域的nil项
+// PrepareRewrite在页面引用确定后填充导航动作，不得提前写出PDF
+type WriteOptions struct {
+	Images         [][]image.Image
+	Text           []TextPage
+	Links          map[int][]*pdfgo.LinkRegion
+	ExactImages    bool
+	ExactText      bool
+	Optimization   pdfgo.OptimizeOptions
+	PrepareRewrite func(context.Context, *pdfgo.Reader, []pdfgo.Reference, *pdfgo.RewriteOptions) error
+}
+
+// Write 合并图像、文字、导航修正及压缩，直接写出最终PDF
+// 入参: ctx 取消上下文, data 后端PDF数据, writer 输出流, settings 写出配置
+// 返回: error 资源、压缩或写入错误
+func Write(ctx context.Context, data []byte, writer io.Writer, settings WriteOptions) error {
+	nativeWrite := settings.PrepareRewrite != nil
+	if !settings.ExactImages && !settings.ExactText && !nativeWrite && settings.Optimization.Compression.Mode == pdfgo.CompressionUnchanged {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		n, err := writer.Write(data)
+		if err == nil && n != len(data) {
+			err = io.ErrShortWrite
+		}
+		return err
+	}
+	reader, err := pdfgo.NewReader(bytes.NewReader(data), int64(len(data)))
+	if err != nil {
+		return err
+	}
+	defer reader.Close()
+	if !settings.ExactImages && !settings.ExactText && !nativeWrite {
+		_, err := reader.OptimizeTo(ctx, writer, settings.Optimization)
+		return err
+	}
+	images := make(map[pdfgo.Reference]image.Image)
+	links := make(map[pdfgo.AnnotationLocation]pdfgo.LinkRegion)
+	texts := make(map[pdfgo.Reference][]pdfgo.TextReplacement)
+	references := make([]pdfgo.Reference, len(settings.Images))
+	pages := 0
+	err = reader.WalkPages(ctx, func(index int, page *pdfgo.Page) error {
+		if index >= len(settings.Images) {
+			return fmt.Errorf("unexpected PDF output page")
+		}
+		pages++
+		references[index] = page.Reference
+		if nativeWrite {
+			annotations, err := page.AnnotationsContext(ctx)
+			if err != nil {
+				return err
+			}
+			expected := settings.Links[index]
+			if len(annotations) != len(expected) {
+				return fmt.Errorf("PDF output link count differs")
+			}
+			for i, link := range expected {
+				if annotations[i].Subtype != pdfgo.Name("Link") {
+					return fmt.Errorf("unexpected PDF output annotation")
+				}
+				if link != nil {
+					links[pdfgo.AnnotationLocation{Page: page.Reference, Index: i}] = *link
+				}
+			}
+		}
+		if !settings.ExactImages && !settings.ExactText {
+			return nil
+		}
+		value, err := reader.Resolve(page.Resources["XObject"])
+		if err != nil {
+			return err
+		}
+		resources, _ := value.(pdfgo.Dictionary)
+		var content bytes.Buffer
+		if _, err := page.WriteContent(ctx, &content); err != nil {
+			return err
+		}
+		position := 0
+		textCount := 0
+		if err := pdfgo.WalkOperations(ctx, content.Bytes(), func(operation pdfgo.Operation) error {
+			if operation.Operator == "BT" {
+				textCount++
+			}
+			if !settings.ExactImages {
+				return nil
+			}
+			if operation.Operator != "Do" {
+				return nil
+			}
+			if len(operation.Operands) != 1 || position >= len(settings.Images[index]) {
+				return fmt.Errorf("unexpected PDF output image")
+			}
+			name, ok := operation.Operands[0].(pdfgo.Name)
+			if !ok {
+				return fmt.Errorf("invalid PDF output image name")
+			}
+			ref, ok := resources[name].(pdfgo.Reference)
+			if !ok {
+				return fmt.Errorf("invalid PDF output image reference")
+			}
+			original := settings.Images[index][position]
+			position++
+			if original == nil {
+				return nil
+			}
+			image, err := reader.ReadImage(ref)
+			if err != nil {
+				return err
+			}
+			if image.Width != original.Bounds().Dx() || image.Height != original.Bounds().Dy() {
+				return fmt.Errorf("PDF output image dimensions differ")
+			}
+			if previous := images[ref]; previous != nil && previous != original {
+				return fmt.Errorf("PDF output image reference conflicts")
+			}
+			images[ref] = original
+			return nil
+		}); err != nil {
+			return err
+		}
+		if settings.ExactImages && position != len(settings.Images[index]) {
+			return fmt.Errorf("PDF output image missing")
+		}
+		if settings.ExactText {
+			if index >= len(settings.Text) || textCount != settings.Text[index].Count {
+				return fmt.Errorf("PDF output text count differs")
+			}
+			if len(settings.Text[index].Replacements) != 0 {
+				texts[page.Reference] = settings.Text[index].Replacements
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	if pages != len(settings.Images) {
+		return fmt.Errorf("PDF output page missing")
+	}
+	options := pdfgo.RewriteOptions{Images: images, ImageOptions: pdfgo.ImageWriteOptions{PreblendBinary: true}, LinkRegions: links, TextReplacements: texts, Optimization: settings.Optimization}
+	if nativeWrite {
+		if err := settings.PrepareRewrite(ctx, reader, references, &options); err != nil {
+			return err
+		}
+	}
+	for ref, original := range images {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		pixels, err := baseimage.PixelDataContext(ctx, original)
+		if err != nil {
+			return err
+		}
+		if pixels == nil || pixels.Bounds() != original.Bounds() {
+			return fmt.Errorf("PDF output image pixel bounds differ")
+		}
+		images[ref] = pixels
+	}
+	_, err = reader.RewriteTo(ctx, writer, options)
+	return err
+}

internal/codec/pdf/font.go

@@ -0,0 +1,338 @@
+// 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 pdf
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/binary"
+	"fmt"
+	"unicode/utf16"
+
+	basefont "github.com/xiaoqidun/ofdgo/internal/base/font"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// FontRepair 保存字体封装修复范围，不混用字形度量与位置索引
+type FontRepair struct {
+	MetricsLimit uint16
+	Locations    bool
+}
+
+// EmbeddedFontName 去除标准六位大写子集前缀，保留字体名称和样式后缀
+// 入参: name PDF或内嵌字体名称
+// 返回: string 原字体名称
+func EmbeddedFontName(name string) string {
+	if len(name) <= 7 || name[6] != '+' {
+		return name
+	}
+	for i := range 6 {
+		if name[i] < 'A' || name[i] > 'Z' {
+			return name
+		}
+	}
+	return name[7:]
+}
+
+// FontProgram 为PDF子集字体补齐封装表，保留字形轮廓和编号
+// 无效字符表按PDF已解码字形重建，不改变字符对应的字形编号
+// 入参: source PDF字体, type1 已解析的Type1程序，nil时按需解析
+// 返回: []byte 封装后的字体数据, FontRepair 字体修复范围, error 错误信息
+func FontProgram(source *pdfgo.Font, type1 *basefont.Type1Program) ([]byte, FontRepair, error) {
+	var repair FontRepair
+	program := source.Program
+	if source.ProgramType == "FontFile" {
+		if type1 == nil {
+			parsed, err := basefont.ParseType1Program(program)
+			if err != nil {
+				return nil, repair, err
+			}
+			type1 = &parsed
+		}
+		var err error
+		program, err = type1.ToCFF(FontIdentity(source))
+		if err != nil {
+			return nil, repair, err
+		}
+	}
+	bareCFF := len(program) >= 4 && program[0] == 1 && program[1] == 0 && program[2] >= 4 && program[3] >= 1 && program[3] <= 4
+	if source.ProgramType == "Type1C" || source.ProgramType == "CIDFontType0C" || bareCFF {
+		var err error
+		program, _, err = basefont.WrapCFFToOTF(program)
+		if err != nil {
+			return nil, repair, err
+		}
+	}
+	tables, err := basefont.FileTables(program, 0)
+	if err != nil {
+		return nil, repair, err
+	}
+	if len(tables["head"]) < 54 || len(tables["maxp"]) < 6 || len(tables["hhea"]) < 36 || len(tables["hmtx"]) == 0 {
+		return nil, repair, fmt.Errorf("embedded PDF font lacks required metrics")
+	}
+	count := binary.BigEndian.Uint16(tables["maxp"][4:6])
+	if count == 0 {
+		return nil, repair, fmt.Errorf("embedded PDF font has no glyphs")
+	}
+	repair.Locations, err = basefont.NormalizeTrueTypeLocations(tables)
+	if err != nil {
+		return nil, repair, err
+	}
+	changed := repair.Locations
+	if head := tables["head"]; len(head) == 56 && binary.BigEndian.Uint32(head[:4]) == 0x00010000 && head[54] == 0 && head[55] == 0 {
+		tables["head"] = head[:54]
+		changed = true
+	}
+	if cff := tables["CFF "]; len(cff) != 0 {
+		sanitized, err := basefont.SanitizeCFF(cff)
+		if err != nil {
+			return nil, repair, err
+		}
+		normalized, err := basefont.NormalizeCFFCharstringsAt(sanitized, binary.BigEndian.Uint16(tables["head"][18:20]))
+		if err != nil {
+			return nil, repair, err
+		}
+		if !bytes.Equal(normalized, cff) {
+			tables["CFF "] = normalized
+			changed = true
+		}
+	}
+	metrics := int(binary.BigEndian.Uint16(tables["hhea"][34:36]))
+	if metrics == 0 || metrics > int(count) {
+		return nil, repair, fmt.Errorf("invalid embedded PDF font metric count")
+	}
+	metricLength := 4*metrics + 2*(int(count)-metrics)
+	if len(tables["hmtx"]) < metricLength {
+		if len(tables["hmtx"]) < 4*metrics || len(tables["hmtx"])%2 != 0 {
+			return nil, repair, fmt.Errorf("incomplete embedded PDF font metrics: have %d, need %d", len(tables["hmtx"]), metricLength)
+		}
+		limit := metrics + (len(tables["hmtx"])-4*metrics)/2
+		missing, err := missingLeftBearings(tables, limit, int(count))
+		if err != nil {
+			return nil, repair, err
+		}
+		tables["hmtx"] = append(bytes.Clone(tables["hmtx"]), missing...)
+		repair.MetricsLimit = uint16(limit)
+		changed = true
+	}
+	if len(tables["hmtx"]) > metricLength {
+		tables["hmtx"] = tables["hmtx"][:metricLength]
+		changed = true
+	}
+	invalidCmap := false
+	if source.Subtype == "TrueType" || source.Subtype == "Type0" {
+		mapping := basefont.ParseCmapMappings(tables["cmap"])
+		for char, glyph := range mapping {
+			if glyph >= count {
+				delete(mapping, char)
+				invalidCmap = true
+			}
+		}
+		if invalidCmap && source.Subtype == "TrueType" {
+			tables["cmap"] = basefont.BuildCmapTable(count, mapping)
+			changed = true
+		}
+	}
+	if len(tables["cmap"]) == 0 || source.Subtype == "Type0" && invalidCmap || (source.Subtype == "Type0" || source.Subtype == "TrueType") && CmapNeedsRebuild(tables["cmap"]) {
+		mapping, err := source.GlyphMap()
+		if err != nil {
+			return nil, repair, err
+		}
+		for _, glyph := range mapping {
+			if glyph >= count {
+				return nil, repair, fmt.Errorf("PDF font glyph %d exceeds glyph count %d", glyph, count)
+			}
+		}
+		basefont.AddPackedGlyphMapping(mapping, count)
+		tables["cmap"] = basefont.BuildCmapTable(count, mapping)
+		changed = true
+	}
+	if len(basefont.NamesFromTable(tables["name"])) == 0 {
+		fontName := FontIdentity(source)
+		name := utf16.Encode([]rune(fontName))
+		if len(name) > 32767 {
+			return nil, repair, fmt.Errorf("PDF font name exceeds name table capacity")
+		}
+		data := make([]byte, 42+len(name)*2)
+		binary.BigEndian.PutUint16(data[2:], 3)
+		binary.BigEndian.PutUint16(data[4:], 42)
+		for n, id := range []uint16{1, 4, 6} {
+			record := data[6+n*12:]
+			binary.BigEndian.PutUint16(record, 3)
+			binary.BigEndian.PutUint16(record[2:], 1)
+			binary.BigEndian.PutUint16(record[4:], 0x409)
+			binary.BigEndian.PutUint16(record[6:], id)
+			binary.BigEndian.PutUint16(record[8:], uint16(len(name)*2))
+		}
+		for n, v := range name {
+			binary.BigEndian.PutUint16(data[42+n*2:], v)
+		}
+		tables["name"] = data
+		changed = true
+	}
+	if len(tables["post"]) == 0 {
+		tables["post"] = basefont.BuildPostTable()
+		changed = true
+	}
+	if len(tables["OS/2"]) == 0 {
+		hhea := tables["hhea"]
+		tables["OS/2"] = basefont.BuildOS2TableWithMetrics(int16(binary.BigEndian.Uint16(hhea[4:6])), int16(binary.BigEndian.Uint16(hhea[6:8])))
+		changed = true
+	}
+	for _, tag := range []string{"cvt ", "fpgm", "prep"} {
+		if data, ok := tables[tag]; ok && len(data) == 0 {
+			delete(tables, tag)
+			changed = true
+		}
+	}
+	if !changed && !sfntMissingPadding(program) {
+		return program, repair, nil
+	}
+	result, err := basefont.SerializeOTF(tables)
+	return result, repair, err
+}
+
+// FontIdentity 返回字体名称或由原始程序生成的稳定封装标识
+// 入参: source PDF字体
+// 返回: string 字体标识
+func FontIdentity(source *pdfgo.Font) string {
+	if source.Name != "" {
+		return source.Name
+	}
+	checksum := sha256.Sum256(source.Program)
+	return fmt.Sprintf("PDF-%x", checksum[:28])
+}
+
+// CmapNeedsRebuild 检查字体封装字符表是否存在结构错误或交叠区段
+// 入参: data cmap表数据
+// 返回: bool 是否需要按PDF显式字形编号重建
+func CmapNeedsRebuild(data []byte) bool {
+	if len(data) < 4 || binary.BigEndian.Uint16(data) != 0 {
+		return true
+	}
+	count := int(binary.BigEndian.Uint16(data[2:]))
+	if count == 0 || count > (len(data)-4)/8 {
+		return true
+	}
+	for index := range count {
+		offset := uint64(binary.BigEndian.Uint32(data[8+8*index:]))
+		if offset < uint64(4+8*count) || offset > uint64(len(data)) || uint64(len(data))-offset < 2 {
+			return true
+		}
+		sub := data[int(offset):]
+		if binary.BigEndian.Uint16(sub) == 6 {
+			if len(sub) < 10 {
+				return true
+			}
+			length := int(binary.BigEndian.Uint16(sub[2:]))
+			first, glyphs := int(binary.BigEndian.Uint16(sub[6:])), int(binary.BigEndian.Uint16(sub[8:]))
+			if length%2 != 0 || length > len(sub) || 10+2*glyphs > length || first+glyphs > 65536 {
+				return true
+			}
+			continue
+		}
+		if binary.BigEndian.Uint16(sub) != 4 {
+			continue
+		}
+		if len(sub) < 16 {
+			return true
+		}
+		length := int(binary.BigEndian.Uint16(sub[2:]))
+		segmentBytes := int(binary.BigEndian.Uint16(sub[6:]))
+		segments := segmentBytes / 2
+		if segmentBytes == 0 || segmentBytes%2 != 0 || length%2 != 0 || length > len(sub) || 16+8*segments > length {
+			return true
+		}
+		glyphStart := 16 + 8*segments
+		previous := -1
+		for i := 0; i < segments; i++ {
+			end := int(binary.BigEndian.Uint16(sub[14+2*i:]))
+			start := int(binary.BigEndian.Uint16(sub[16+2*segments+2*i:]))
+			if end < start || start <= previous || i == segments-1 && (start != 65535 || end != 65535) {
+				return true
+			}
+			previous = end
+			position := 16 + 6*segments + 2*i
+			offset := int(binary.BigEndian.Uint16(sub[position:]))
+			if offset != 0 && (offset%2 != 0 || position+offset < glyphStart || position+offset+2*(end-start+1) > length) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// sfntMissingPadding 判断字体表目录是否引用了未写入的末尾对齐字节
+// 入参: program OpenType字体数据
+// 返回: bool 是否需要重新封装
+func sfntMissingPadding(program []byte) bool {
+	if len(program) < 12 {
+		return true
+	}
+	count := int(binary.BigEndian.Uint16(program[4:6]))
+	if count > (len(program)-12)/16 {
+		return true
+	}
+	for index := range count {
+		record := program[12+16*index:]
+		offset := int(binary.BigEndian.Uint32(record[8:12]))
+		length := int(binary.BigEndian.Uint32(record[12:16]))
+		if offset > len(program) || length > len(program)-offset || (4-length%4)%4 > len(program)-offset-length {
+			return true
+		}
+	}
+	return false
+}
+
+// missingLeftBearings 从轮廓边界恢复缺失的尾部左侧边距
+// 入参: tables 字体表, start 首个缺失字形, count 字形总数
+// 返回: []byte 补齐的hmtx数据, error 无法读取轮廓
+func missingLeftBearings(tables map[string][]byte, start, count int) ([]byte, error) {
+	head, loca, glyf := tables["head"], tables["loca"], tables["glyf"]
+	if len(head) < 54 || len(glyf) == 0 {
+		return nil, fmt.Errorf("embedded PDF font lacks glyph outlines for missing metrics")
+	}
+	format := int(int16(binary.BigEndian.Uint16(head[50:52])))
+	entrySize := 2
+	if format == 1 {
+		entrySize = 4
+	} else if format != 0 {
+		return nil, fmt.Errorf("invalid embedded PDF font location format")
+	}
+	if len(loca) < (count+1)*entrySize {
+		return nil, fmt.Errorf("incomplete embedded PDF font glyph locations")
+	}
+	location := func(index int) int {
+		if format == 0 {
+			return int(binary.BigEndian.Uint16(loca[index*2:])) * 2
+		}
+		return int(binary.BigEndian.Uint32(loca[index*4:]))
+	}
+	result := make([]byte, 2*(count-start))
+	for index := start; index < count; index++ {
+		from, to := location(index), location(index+1)
+		if from > to || to > len(glyf) {
+			return nil, fmt.Errorf("invalid embedded PDF font glyph location")
+		}
+		if from == to {
+			continue
+		}
+		if to-from < 10 {
+			return nil, fmt.Errorf("incomplete embedded PDF font glyph outline")
+		}
+		copy(result[(index-start)*2:], glyf[from+2:from+4])
+	}
+	return result, nil
+}

internal/codec/pdf/geometry.go

@@ -0,0 +1,101 @@
+// 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 pdf
+
+import (
+	"context"
+	"fmt"
+
+	basegeom "github.com/xiaoqidun/ofdgo/internal/base/geom"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// GeometryPath 直接转换PDF路径坐标，不经文本编码或曲线展平
+// 入参: ctx 取消上下文, source PDF路径, matrix 坐标变换
+// 返回: basegeom.Path 独立几何路径, error 指令、坐标或取消错误
+func GeometryPath(ctx context.Context, source pdfgo.Path, matrix pdfgo.Matrix) (basegeom.Path, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	path := make(basegeom.Path, len(source.Segments))
+	for i, segment := range source.Segments {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		var count int
+		switch segment.Operator {
+		case "M":
+			path[i].Verb, count = basegeom.Move, 1
+		case "L":
+			path[i].Verb, count = basegeom.Line, 1
+		case "B":
+			path[i].Verb, count = basegeom.Cubic, 3
+		case "C":
+			path[i].Verb = basegeom.ClosePath
+		default:
+			return nil, fmt.Errorf("invalid PDF path operator %q", segment.Operator)
+		}
+		if len(segment.Points) != count {
+			return nil, fmt.Errorf("invalid PDF path operands for %s", segment.Operator)
+		}
+		var points [3]basegeom.Point
+		for j, point := range segment.Points {
+			point = matrix.Apply(point)
+			points[j] = basegeom.Point{X: point.X, Y: point.Y}
+		}
+		if count != 0 {
+			path[i].End = points[count-1]
+		}
+		if count == 3 {
+			path[i].Control1, path[i].Control2 = points[0], points[1]
+		}
+	}
+	if err := path.Validate(); err != nil {
+		return nil, err
+	}
+	return path, ctx.Err()
+}
+
+// GlyphPath 将字形轮廓变换到PDF页面坐标，二次曲线精确转换为三次曲线
+// 入参: outline 字形轮廓, matrix 字形到页面的变换
+// 返回: pdfgo.Path 页面路径, error 非字体轮廓指令
+func GlyphPath(outline basegeom.Path, matrix pdfgo.Matrix) (pdfgo.Path, error) {
+	path := pdfgo.Path{Segments: make([]pdfgo.Segment, 0, len(outline))}
+	var current, start basegeom.Point
+	point := func(p basegeom.Point) pdfgo.Point { return matrix.Apply(pdfgo.Point{X: p.X, Y: p.Y}) }
+	for _, segment := range outline {
+		switch segment.Verb {
+		case basegeom.Move:
+			start = segment.End
+			path.Segments = append(path.Segments, pdfgo.Segment{Operator: "M", Points: []pdfgo.Point{point(segment.End)}})
+		case basegeom.Line:
+			path.Segments = append(path.Segments, pdfgo.Segment{Operator: "L", Points: []pdfgo.Point{point(segment.End)}})
+		case basegeom.Quad:
+			c1 := basegeom.Point{X: current.X + (segment.Control1.X-current.X)*2/3, Y: current.Y + (segment.Control1.Y-current.Y)*2/3}
+			c2 := basegeom.Point{X: segment.End.X + (segment.Control1.X-segment.End.X)*2/3, Y: segment.End.Y + (segment.Control1.Y-segment.End.Y)*2/3}
+			path.Segments = append(path.Segments, pdfgo.Segment{Operator: "B", Points: []pdfgo.Point{point(c1), point(c2), point(segment.End)}})
+		case basegeom.Cubic:
+			path.Segments = append(path.Segments, pdfgo.Segment{Operator: "B", Points: []pdfgo.Point{point(segment.Control1), point(segment.Control2), point(segment.End)}})
+		case basegeom.ClosePath:
+			path.Segments = append(path.Segments, pdfgo.Segment{Operator: "C"})
+			current = start
+			continue
+		default:
+			return pdfgo.Path{}, fmt.Errorf("unsupported PDF glyph geometry verb %d", segment.Verb)
+		}
+		current = segment.End
+	}
+	return path, nil
+}

internal/codec/pdf/image.go

@@ -0,0 +1,95 @@
+// 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 pdf
+
+import (
+	"image"
+	"image/color"
+	"math"
+
+	baseimage "github.com/xiaoqidun/ofdgo/internal/base/image"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// StencilImage 按当前填充色读取模板图像，不分配整幅彩色样本
+type StencilImage struct {
+	Source image.Image
+	Fill   color.NRGBA64
+}
+
+// NativeImage 按源像素输出原生过程色，不分配完整显示颜色缓冲
+type NativeImage struct {
+	Source *pdfgo.ImageProcess
+	Space  *pdfgo.ColorSpace
+}
+
+// ColorModel 保留填充色和模板的有效采样精度
+// 返回: color.Model 非预乘颜色模型
+func (s *StencilImage) ColorModel() color.Model {
+	model := s.Source.ColorModel()
+	if s.Fill.R%257 == 0 && s.Fill.G%257 == 0 && s.Fill.B%257 == 0 && (model == color.GrayModel || model == color.NRGBAModel || model == color.RGBAModel) {
+		return color.NRGBAModel
+	}
+	return color.NRGBA64Model
+}
+
+// Bounds 返回模板图像的采样边界
+// 返回: image.Rectangle 图像边界
+func (s *StencilImage) Bounds() image.Rectangle { return s.Source.Bounds() }
+
+// At 以模板灰度计算填充覆盖率，不重复变换颜色
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.Color 非预乘颜色
+func (s *StencilImage) 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 *StencilImage) NRGBA64At(x, y int) color.NRGBA64 {
+	if !image.Pt(x, y).In(s.Bounds()) {
+		return color.NRGBA64{}
+	}
+	gray := baseimage.NRGBA64At(s.Source, x, y)
+	pixel := s.Fill
+	pixel.A = uint16(65535 - gray.R)
+	return pixel
+}
+
+// ColorModel 保留16位原生分量与源透明度
+// 返回: color.Model 非预乘颜色模型
+func (s *NativeImage) ColorModel() color.Model { return color.NRGBA64Model }
+
+// Bounds 返回源图像的完整采样边界
+// 返回: image.Rectangle 原始像素边界
+func (s *NativeImage) Bounds() image.Rectangle { return s.Source.Bounds() }
+
+// At 获取按OFD输出映射的原生颜色
+// 入参: x 横坐标, y 纵坐标
+// 返回: color.Color 非预乘颜色
+func (s *NativeImage) At(x, y int) color.Color { return s.NRGBA64At(x, y) }
+
+// NRGBA64At 按原始精度转换设备过程色，不进行页面采样或备用变换
+// 入参: x 横坐标, y 纵坐标
+// 返回: color.NRGBA64 非预乘颜色
+func (s *NativeImage) NRGBA64At(x, y int) color.NRGBA64 {
+	if !image.Pt(x, y).In(s.Bounds()) {
+		return color.NRGBA64{}
+	}
+	values, alpha := s.Source.ValuesAt(x, y)
+	rgb, _ := OutputColor(s.Space, values)
+	return color.NRGBA64{R: uint16(math.Round(rgb[0] * 65535)), G: uint16(math.Round(rgb[1] * 65535)), B: uint16(math.Round(rgb[2] * 65535)), A: uint16(math.Round(alpha * 65535))}
+}

internal/codec/pdf/image_cache.go

@@ -0,0 +1,106 @@
+// 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 pdf
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"reflect"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// imageValueBudget 限制图像描述的检查深度和保留字节数
+type imageValueBudget struct {
+	nodes int
+	bytes int
+}
+
+// ImageDigest 对无间接依赖的小图像生成编码摘要，超预算时不参与内容缓存
+// 入参: ctx 取消上下文, source 图像描述
+// 返回: [32]byte 编码摘要, bool 是否可复用, error 取消错误
+func ImageDigest(ctx context.Context, source *pdfgo.Image) ([32]byte, bool, error) {
+	if source == nil || source.Stream == nil || len(source.Stream.Data) > 1<<20 {
+		return [32]byte{}, false, nil
+	}
+	budget := imageValueBudget{nodes: 256, bytes: 65536}
+	for _, value := range []pdfgo.Object{source.Stream.Dictionary, source.ColorSpace, source.Decode, source.Mask, source.SoftMask} {
+		if !imageDirectValue(value, &budget) {
+			return [32]byte{}, false, ctx.Err()
+		}
+	}
+	hash := sha256.New()
+	data := source.Stream.Data
+	for len(data) != 0 {
+		if err := ctx.Err(); err != nil {
+			return [32]byte{}, false, err
+		}
+		n := min(len(data), 65536)
+		hash.Write(data[:n])
+		data = data[n:]
+	}
+	var result [32]byte
+	hash.Sum(result[:0])
+	return result, true, ctx.Err()
+}
+
+// SameImage 核对完整编码与有效图像属性，不以摘要相同代替内容相同
+// 入参: left 已缓存图像, right 待复用图像，二者须包含有效编码流
+// 返回: bool 是否可使用同一图像资源
+func SameImage(left, right *pdfgo.Image) bool {
+	return left.Width == right.Width && left.Height == right.Height && left.BitsPerComponent == right.BitsPerComponent &&
+		left.ImageMask == right.ImageMask && left.Interpolate == right.Interpolate &&
+		bytes.Equal(left.Stream.Data, right.Stream.Data) && reflect.DeepEqual(left.Stream.Dictionary, right.Stream.Dictionary) &&
+		reflect.DeepEqual(left.ColorSpace, right.ColorSpace) && reflect.DeepEqual(left.Decode, right.Decode) &&
+		reflect.DeepEqual(left.Mask, right.Mask) && reflect.DeepEqual(left.SoftMask, right.SoftMask)
+}
+
+// imageDirectValue 检查图像描述是否完全独立，拒绝间接引用和嵌套流
+// 入参: value 描述值, budget 描述检查预算
+// 返回: bool 是否不依赖阅读器资源
+func imageDirectValue(value pdfgo.Object, budget *imageValueBudget) bool {
+	if budget.nodes <= 0 || budget.bytes < 64 {
+		return false
+	}
+	budget.nodes--
+	budget.bytes -= 64
+	switch v := value.(type) {
+	case nil, pdfgo.Boolean, pdfgo.Integer, pdfgo.Real:
+		return true
+	case pdfgo.Name:
+		budget.bytes -= len(v)
+		return budget.bytes >= 0
+	case pdfgo.String:
+		budget.bytes -= len(v)
+		return budget.bytes >= 0
+	case pdfgo.Array:
+		for _, child := range v {
+			if !imageDirectValue(child, budget) {
+				return false
+			}
+		}
+		return true
+	case pdfgo.Dictionary:
+		for key, child := range v {
+			budget.bytes -= len(key)
+			if !imageDirectValue(child, budget) {
+				return false
+			}
+		}
+		return true
+	}
+	return false
+}

internal/codec/pdf/link.go

@@ -0,0 +1,444 @@
+// 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 pdf
+
+import (
+	"context"
+	"fmt"
+	"math"
+	"slices"
+
+	"github.com/tdewolff/canvas"
+	basegeom "github.com/xiaoqidun/ofdgo/internal/base/geom"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// PDF链接区域细分上限与曲线逼近误差，误差单位为毫米
+const (
+	LinkEdgeLimit = 4096
+	LinkQuadLimit = 65536
+	linkTolerance = 0.01
+)
+
+// linkEdge 保存按纵坐标排序的边及原始绕行方向
+type linkEdge struct {
+	a, b    pdfgo.Point
+	winding int
+}
+
+// linkCross 保存水平扫描线与区域边的交点
+type linkCross struct {
+	x    float64
+	edge int
+}
+
+// ActionRegion 将非零绕行区域分解为PDF链接四边形，保留空洞和相交轮廓
+// 入参: ctx 取消上下文, outline 页面SVG路径, pageH 页面高度
+// 返回: *pdfgo.LinkRegion 链接区域，nil表示沿用矩形, error 解析或复杂度错误
+func ActionRegion(ctx context.Context, outline string, pageH float64) (*pdfgo.LinkRegion, error) {
+	if outline == "" {
+		return nil, nil
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	path, err := canvas.ParseSVGPath(outline)
+	if err != nil {
+		return nil, err
+	}
+	if path.Len() > LinkEdgeLimit {
+		return nil, fmt.Errorf("PDF link region exceeds edge limit")
+	}
+	if _, ok := basegeom.RectangleBounds(linkGeometry(path)); ok {
+		return nil, nil
+	}
+	path, err = FlattenLink(ctx, path)
+	if err != nil {
+		return nil, err
+	}
+	if quads := convexLink(path, pageH); len(quads) != 0 {
+		return linkRegionBounds(quads), nil
+	}
+	var edges []linkEdge
+	var levels []float64
+	var start, previous pdfgo.Point
+	open := false
+	add := func(a, b pdfgo.Point) {
+		if a.Y == b.Y {
+			return
+		}
+		edge := linkEdge{a: a, b: b, winding: 1}
+		if a.Y > b.Y {
+			edge.a, edge.b, edge.winding = b, a, -1
+		}
+		edges = append(edges, edge)
+		levels = append(levels, edge.a.Y, edge.b.Y)
+	}
+	scanner := path.Scanner()
+	for scanner.Scan() {
+		p := scanner.End()
+		point := pdfgo.Point{X: p.X * 72 / 25.4, Y: (pageH - p.Y) * 72 / 25.4}
+		if !finite(point.X) || !finite(point.Y) {
+			return nil, fmt.Errorf("invalid PDF link coordinate")
+		}
+		switch scanner.Cmd() {
+		case canvas.MoveToCmd:
+			if open {
+				add(previous, start)
+			}
+			start, open = point, true
+		case canvas.LineToCmd:
+			if !open {
+				start, open = previous, true
+			}
+			add(previous, point)
+		case canvas.CloseCmd:
+			add(previous, start)
+			open = false
+		}
+		previous = point
+	}
+	if open {
+		add(previous, start)
+	}
+	for i, a := range edges {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		for _, b := range edges[i+1:] {
+			low, high := max(a.a.Y, b.a.Y), min(a.b.Y, b.b.Y)
+			if low >= high {
+				continue
+			}
+			d0, d1 := a.x(low)-b.x(low), a.x(high)-b.x(high)
+			if d0 < 0 && d1 > 0 || d0 > 0 && d1 < 0 {
+				y := low + (high-low)*(d0/(d0-d1))
+				if !finite(y) {
+					return nil, fmt.Errorf("invalid PDF link intersection")
+				}
+				levels = append(levels, y)
+				if len(levels) > LinkQuadLimit {
+					return nil, fmt.Errorf("PDF link region exceeds intersection limit")
+				}
+			}
+		}
+	}
+	slices.Sort(levels)
+	levels = slices.Compact(levels)
+	region := &pdfgo.LinkRegion{}
+	crossings := make([]linkCross, 0, len(edges))
+	for i := 1; i < len(levels); i++ {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		low, high := levels[i-1], levels[i]
+		mid := low + (high-low)/2
+		if mid <= low || mid >= high {
+			continue
+		}
+		crossings = crossings[:0]
+		for j, edge := range edges {
+			if edge.a.Y < mid && mid < edge.b.Y {
+				crossings = append(crossings, linkCross{edge.x(mid), j})
+			}
+		}
+		slices.SortFunc(crossings, func(a, b linkCross) int {
+			if a.x < b.x {
+				return -1
+			}
+			if a.x > b.x {
+				return 1
+			}
+			return a.edge - b.edge
+		})
+		winding, left := 0, 0
+		for _, cross := range crossings {
+			before := winding
+			winding += edges[cross.edge].winding
+			if before == 0 && winding != 0 {
+				left = cross.edge
+			}
+			if before != 0 && winding == 0 {
+				a, b := edges[left], edges[cross.edge]
+				quad := [4]pdfgo.Point{{X: a.x(low), Y: low}, {X: b.x(low), Y: low}, {X: b.x(high), Y: high}, {X: a.x(high), Y: high}}
+				region.Quads = appendLinkQuad(region.Quads, quad)
+				if len(region.Quads) > LinkQuadLimit {
+					return nil, fmt.Errorf("PDF link region exceeds quadrilateral limit")
+				}
+			}
+		}
+	}
+	if len(region.Quads) == 0 {
+		return region, nil
+	}
+	return linkRegionBounds(region.Quads), nil
+}
+
+// convexLink 直接保留单个凸四边形，三角形只分成三个四边形
+// 入参: path 已展开路径, pageH 页面高度
+// 返回: [][4]pdfgo.Point 逆时针四边形，不适用时为空
+func convexLink(path *canvas.Path, pageH float64) [][4]pdfgo.Point {
+	if path.HasSubpaths() || path.Len() > 6 {
+		return nil
+	}
+	points := path.Coords()
+	if len(points) > 1 && points[0] == points[len(points)-1] {
+		points = points[:len(points)-1]
+	}
+	if len(points) < 3 || len(points) > 4 {
+		return nil
+	}
+	var storage [4]pdfgo.Point
+	vertices := storage[:len(points)]
+	for i, p := range points {
+		vertices[i] = pdfgo.Point{X: p.X * 72 / 25.4, Y: (pageH - p.Y) * 72 / 25.4}
+	}
+	direction := 0.0
+	for i, a := range vertices {
+		b, c := vertices[(i+1)%len(vertices)], vertices[(i+2)%len(vertices)]
+		cross := linkTurn(a, b, c)
+		if !finite(cross) || cross == 0 || direction != 0 && (direction < 0) != (cross < 0) {
+			return nil
+		}
+		direction = cross
+	}
+	if direction < 0 {
+		slices.Reverse(vertices)
+	}
+	if len(vertices) == 4 {
+		return [][4]pdfgo.Point{storage}
+	}
+	return appendLinkTriangle(nil, [3]pdfgo.Point{vertices[0], vertices[1], vertices[2]})
+}
+
+// linkRegionBounds 计算四边形共同的注解矩形，保证全部顶点落在矩形内
+// 入参: quads 链接四边形
+// 返回: *pdfgo.LinkRegion 链接区域
+func linkRegionBounds(quads [][4]pdfgo.Point) *pdfgo.LinkRegion {
+	region := &pdfgo.LinkRegion{Quads: quads, Rect: pdfgo.Rectangle{XMin: math.Inf(1), YMin: math.Inf(1), XMax: math.Inf(-1), YMax: math.Inf(-1)}}
+	for _, quad := range quads {
+		for _, p := range quad {
+			region.Rect.XMin, region.Rect.YMin = min(region.Rect.XMin, p.X), min(region.Rect.YMin, p.Y)
+			region.Rect.XMax, region.Rect.YMax = max(region.Rect.XMax, p.X), max(region.Rect.YMax, p.Y)
+		}
+	}
+	return region
+}
+
+// FlattenLink 在取消和数量限制内展开动作曲线，复用标准椭圆弧转换
+// 入参: ctx 取消上下文, path 页面SVG路径
+// 返回: *canvas.Path 闭合折线路径, error 精度或复杂度错误
+func FlattenLink(ctx context.Context, path *canvas.Path) (*canvas.Path, error) {
+	geometry := linkGeometry(path)
+	result := &canvas.Path{}
+	var current, start basegeom.Point
+	count := 0
+	var flatten func([]basegeom.Point, int) error
+	flatten = func(points []basegeom.Point, depth int) error {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		first, last := points[0], points[len(points)-1]
+		dx, dy := last.X-first.X, last.Y-first.Y
+		length := math.Hypot(dx, dy)
+		distance := 0.0
+		for _, point := range points[1 : len(points)-1] {
+			t := 0.0
+			if length > 0 {
+				t = min(max((point.X-first.X)*(dx/length)+(point.Y-first.Y)*(dy/length), 0), length) / length
+			}
+			distance = max(distance, math.Hypot(point.X-(first.X*(1-t)+last.X*t), point.Y-(first.Y*(1-t)+last.Y*t)))
+		}
+		if !finite(length) || !finite(distance) {
+			return fmt.Errorf("invalid PDF link curve")
+		}
+		if distance <= linkTolerance/2 {
+			count++
+			if count > LinkEdgeLimit {
+				return fmt.Errorf("PDF link region exceeds edge limit")
+			}
+			result.LineTo(last.X, -last.Y)
+			return nil
+		}
+		if depth == 32 {
+			return fmt.Errorf("PDF link curve tolerance cannot be met")
+		}
+		var work, left, right [4]basegeom.Point
+		copy(work[:], points)
+		for n := len(points); n > 0; n-- {
+			left[len(points)-n], right[n-1] = work[0], work[n-1]
+			for i := 0; i < n-1; i++ {
+				work[i] = basegeom.Lerp(work[i], work[i+1], .5)
+			}
+		}
+		if err := flatten(left[:len(points)], depth+1); err != nil {
+			return err
+		}
+		return flatten(right[:len(points)], depth+1)
+	}
+	for _, segment := range geometry {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		switch segment.Verb {
+		case basegeom.Move:
+			result.MoveTo(segment.End.X, -segment.End.Y)
+			current, start = segment.End, segment.End
+		case basegeom.ClosePath:
+			result.Close()
+			current = start
+		default:
+			curves := basegeom.Path{segment}
+			if segment.Verb == basegeom.Arc {
+				var err error
+				curves, err = basegeom.ArcCurves(current, segment, linkTolerance/2)
+				if err != nil {
+					return nil, err
+				}
+				if len(curves) > LinkEdgeLimit-count {
+					return nil, fmt.Errorf("PDF link region exceeds edge limit")
+				}
+			}
+			for _, curve := range curves {
+				var storage [4]basegeom.Point
+				points := append(storage[:0], current)
+				if curve.Verb == basegeom.Quad || curve.Verb == basegeom.Cubic {
+					points = append(points, curve.Control1)
+				}
+				if curve.Verb == basegeom.Cubic {
+					points = append(points, curve.Control2)
+				}
+				points = append(points, curve.End)
+				if err := flatten(points, 0); err != nil {
+					return nil, err
+				}
+				current = curve.End
+			}
+		}
+	}
+	return result, nil
+}
+
+// x 计算非水平边在指定纵坐标处的横坐标
+// 入参: y 扫描线纵坐标
+// 返回: float64 交点横坐标
+func (e linkEdge) x(y float64) float64 {
+	t := (y - e.a.Y) / (e.b.Y - e.a.Y)
+	return e.a.X*(1-t) + e.b.X*t
+}
+
+// appendLinkQuad 收集梯形，尖端退化为三角形时细分为三个非退化四边形
+// 入参: quads 已有四边形, quad 扫描带梯形
+// 返回: [][4]pdfgo.Point 四边形集合
+func appendLinkQuad(quads [][4]pdfgo.Point, quad [4]pdfgo.Point) [][4]pdfgo.Point {
+	epsilon := 1e-12
+	for _, point := range quad {
+		epsilon = max(epsilon, math.Abs(point.X)*1e-12, math.Abs(point.Y)*1e-12)
+	}
+	if quad[2].Y-quad[0].Y <= epsilon {
+		return quads
+	}
+	if quad[1].X-quad[0].X <= epsilon {
+		quad[0].X, quad[1].X = (quad[0].X+quad[1].X)/2, (quad[0].X+quad[1].X)/2
+	}
+	if quad[2].X-quad[3].X <= epsilon {
+		quad[3].X, quad[2].X = (quad[3].X+quad[2].X)/2, (quad[3].X+quad[2].X)/2
+	}
+	var triangle [3]pdfgo.Point
+	if quad[0] == quad[1] {
+		if quad[2] == quad[3] {
+			return quads
+		}
+		triangle = [3]pdfgo.Point{quad[0], quad[2], quad[3]}
+	} else if quad[2] == quad[3] {
+		triangle = [3]pdfgo.Point{quad[0], quad[1], quad[2]}
+	} else {
+		return appendValidLinkQuad(quads, quad)
+	}
+	return appendLinkTriangle(quads, triangle)
+}
+
+// appendLinkTriangle 连接三角形重心和边中点，生成覆盖相同区域的凸四边形
+// 入参: quads 已有四边形, triangle 逆时针三角形
+// 返回: [][4]pdfgo.Point 四边形集合
+func appendLinkTriangle(quads [][4]pdfgo.Point, triangle [3]pdfgo.Point) [][4]pdfgo.Point {
+	center := pdfgo.Point{X: (triangle[0].X + triangle[1].X + triangle[2].X) / 3, Y: (triangle[0].Y + triangle[1].Y + triangle[2].Y) / 3}
+	for i, a := range triangle {
+		b, c := triangle[(i+1)%3], triangle[(i+2)%3]
+		quads = appendValidLinkQuad(quads, [4]pdfgo.Point{a, {X: (a.X + b.X) / 2, Y: (a.Y + b.Y) / 2}, center, {X: (a.X + c.X) / 2, Y: (a.Y + c.Y) / 2}})
+	}
+	return quads
+}
+
+// linkTurn 计算相邻边的转向，消除近共线乘积相减产生的舍入噪声
+// 入参: a 前顶点, b 当前顶点, c 后顶点
+// 返回: float64 有向面积的两倍，数值退化时为零
+func linkTurn(a, b, c pdfgo.Point) float64 {
+	u, v := (b.X-a.X)*(c.Y-b.Y), (b.Y-a.Y)*(c.X-b.X)
+	cross := u - v
+	if math.Abs(cross) <= (math.Abs(u)+math.Abs(v))*1e-12 {
+		return 0
+	}
+	return cross
+}
+
+// appendValidLinkQuad 仅保留有限且非退化的逆时针凸四边形
+// 入参: quads 已有四边形, quad 候选四边形
+// 返回: [][4]pdfgo.Point 四边形集合
+func appendValidLinkQuad(quads [][4]pdfgo.Point, quad [4]pdfgo.Point) [][4]pdfgo.Point {
+	for i, a := range quad {
+		cross := linkTurn(a, quad[(i+1)%4], quad[(i+2)%4])
+		if !finite(cross) || cross <= 0 {
+			return quads
+		}
+	}
+	return append(quads, quad)
+}
+
+// linkGeometry 转换画布坐标为基础几何路径，保留曲线和椭圆弧参数
+// 入参: path 画布路径
+// 返回: basegeom.Path 左上角坐标路径
+func linkGeometry(path *canvas.Path) basegeom.Path {
+	if path == nil {
+		return nil
+	}
+	result := make(basegeom.Path, 0, path.Len())
+	scanner := path.Scanner()
+	for scanner.Scan() {
+		end := scanner.End()
+		segment := basegeom.Segment{End: basegeom.Point{X: end.X, Y: -end.Y}}
+		switch scanner.Cmd() {
+		case canvas.MoveToCmd:
+			segment.Verb = basegeom.Move
+		case canvas.LineToCmd:
+			segment.Verb = basegeom.Line
+		case canvas.QuadToCmd:
+			control := scanner.CP1()
+			segment.Verb, segment.Control1 = basegeom.Quad, basegeom.Point{X: control.X, Y: -control.Y}
+		case canvas.CubeToCmd:
+			c1, c2 := scanner.CP1(), scanner.CP2()
+			segment.Verb = basegeom.Cubic
+			segment.Control1, segment.Control2 = basegeom.Point{X: c1.X, Y: -c1.Y}, basegeom.Point{X: c2.X, Y: -c2.Y}
+		case canvas.ArcToCmd:
+			segment.Verb = basegeom.Arc
+			segment.RadiusX, segment.RadiusY, segment.Rotation, segment.Large, segment.Sweep = scanner.Arc()
+			segment.Rotation, segment.Sweep = -segment.Rotation, !segment.Sweep
+		case canvas.CloseCmd:
+			segment.Verb = basegeom.ClosePath
+		}
+		result = append(result, segment)
+	}
+	return result
+}

internal/codec/pdf/media.go

@@ -0,0 +1,162 @@
+// 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 pdf
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"fmt"
+	"math"
+	"net/url"
+	"path"
+	"strings"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// MediaFormat 获取媒体文件扩展名，URL参数和片段不参与格式判断
+// 入参: file PDF文件说明
+// 返回: string 媒体格式，未声明扩展名时为空
+func MediaFormat(file pdfgo.FileSpecification) string {
+	name := strings.ReplaceAll(file.Name, "\\", "/")
+	if file.FileSystem == "URL" {
+		if location, err := url.Parse(name); err == nil {
+			name = location.Path
+		}
+	}
+	return strings.TrimPrefix(path.Ext(name), ".")
+}
+
+// SoundWAV 封装PDF采样音频，保持采样率、声道及数值，超过RIFF容量时使用RF64
+// 入参: ctx 取消上下文, sound 音频流及参数
+// 返回: []byte WAVE文件, error 不可表示的参数或损坏的采样数据
+func SoundWAV(ctx context.Context, sound pdfgo.Sound) ([]byte, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if sound.File != nil || sound.Compression != "" {
+		return nil, &pdfgo.UnsupportedError{Feature: "external or compressed sound samples"}
+	}
+	if sound.Stream == nil || sound.Channels <= 0 || math.IsNaN(sound.Rate) || math.IsInf(sound.Rate, 0) || sound.Rate <= 0 {
+		return nil, fmt.Errorf("invalid sound sample parameters")
+	}
+	if sound.Rate != math.Trunc(sound.Rate) || sound.Rate > math.MaxUint32 || sound.Channels > math.MaxUint16 || sound.Bits != 8 && sound.Bits != 16 && sound.Bits != 24 && sound.Bits != 32 {
+		return nil, &pdfgo.UnsupportedError{Feature: "sound parameters in WAVE"}
+	}
+	format := uint16(1)
+	if sound.Encoding == "muLaw" {
+		format = 7
+	} else if sound.Encoding == "ALaw" {
+		format = 6
+	}
+	if format != 1 && sound.Bits != 8 {
+		return nil, fmt.Errorf("invalid companded sound depth")
+	}
+	width := sound.Bits / 8
+	align := uint64(sound.Channels) * uint64(width)
+	rate := uint64(sound.Rate)
+	if align > math.MaxUint16 || rate*align > math.MaxUint32 {
+		return nil, &pdfgo.UnsupportedError{Feature: "sound block alignment in WAVE"}
+	}
+	data, err := sound.Stream.DecodeContext(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if uint64(len(data))%align != 0 {
+		return nil, fmt.Errorf("incomplete sound sample frame")
+	}
+	if format == 1 {
+		for offset := 0; offset < len(data); offset += width {
+			if offset%(1<<16) == 0 {
+				if err := ctx.Err(); err != nil {
+					return nil, err
+				}
+			}
+			if sound.Encoding == "Raw" && width > 1 || sound.Encoding == "Signed" && width == 1 {
+				data[offset] ^= 0x80
+			}
+			for left, right := offset, offset+width-1; left < right; left, right = left+1, right-1 {
+				data[left], data[right] = data[right], data[left]
+			}
+		}
+	}
+	formatSize := uint32(16)
+	extra := uint64(0)
+	if format == 1 && (sound.Bits > 16 || sound.Channels > 2) {
+		format = 0xfffe
+		formatSize = 40
+		extra = 36
+	} else if format != 1 {
+		formatSize = 18
+		extra = 14
+	}
+	size := uint64(36) + extra + uint64(len(data)) + uint64(len(data)%2)
+	large := size > math.MaxUint32
+	var out bytes.Buffer
+	put16 := func(v uint16) { _ = binary.Write(&out, binary.LittleEndian, v) }
+	put32 := func(v uint32) { _ = binary.Write(&out, binary.LittleEndian, v) }
+	put64 := func(v uint64) { _ = binary.Write(&out, binary.LittleEndian, v) }
+	if large {
+		out.WriteString("RF64")
+		put32(math.MaxUint32)
+		out.WriteString("WAVEds64")
+		put32(28)
+		put64(size + 36)
+		put64(uint64(len(data)))
+		put64(uint64(len(data)) / align)
+		put32(0)
+	} else {
+		out.WriteString("RIFF")
+		put32(uint32(size))
+		out.WriteString("WAVE")
+	}
+	out.WriteString("fmt ")
+	put32(formatSize)
+	put16(format)
+	put16(uint16(sound.Channels))
+	put32(uint32(rate))
+	put32(uint32(rate * align))
+	put16(uint16(align))
+	put16(uint16(sound.Bits))
+	if format != 1 {
+		if format == 0xfffe {
+			put16(22)
+			put16(uint16(sound.Bits))
+			put32(0)
+			out.Write([]byte{1, 0, 0, 0, 0, 0, 0x10, 0, 0x80, 0, 0, 0xaa, 0, 0x38, 0x9b, 0x71})
+		} else {
+			put16(0)
+		}
+		out.WriteString("fact")
+		put32(4)
+		if large {
+			put32(math.MaxUint32)
+		} else {
+			put32(uint32(uint64(len(data)) / align))
+		}
+	}
+	out.WriteString("data")
+	if large {
+		put32(math.MaxUint32)
+	} else {
+		put32(uint32(len(data)))
+	}
+	out.Write(data)
+	if len(data)%2 != 0 {
+		out.WriteByte(0)
+	}
+	return out.Bytes(), ctx.Err()
+}

internal/codec/pdf/number.go

@@ -0,0 +1,26 @@
+// 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 pdf
+
+import (
+	"math"
+)
+
+// finite 判断数值是否有限
+// 入参: value 待检查数值
+// 返回: bool 是否为有限数值
+func finite(value float64) bool {
+	return !math.IsNaN(value) && !math.IsInf(value, 0)
+}

internal/codec/pdf/page.go

@@ -0,0 +1,40 @@
+// 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 pdf
+
+import (
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// PageMatrix 将裁剪框、用户单位及页面旋转转换为OFD毫米坐标
+// 入参: page PDF页面
+// 返回: pdfgo.Matrix 坐标变换, float64 页面宽度, float64 页面高度
+func PageMatrix(page *pdfgo.Page) (pdfgo.Matrix, float64, float64) {
+	b := page.CropBox
+	scale := 25.4 / 72 * page.UserUnit
+	width, height := (b.XMax-b.XMin)*scale, (b.YMax-b.YMin)*scale
+	m := pdfgo.Matrix{scale, 0, 0, -scale, -b.XMin * scale, b.YMax * scale}
+	switch page.Rotation {
+	case 90:
+		m = pdfgo.Matrix{0, 1, -1, 0, height, 0}.Mul(m)
+		width, height = height, width
+	case 180:
+		m = pdfgo.Matrix{-1, 0, 0, -1, width, height}.Mul(m)
+	case 270:
+		m = pdfgo.Matrix{0, -1, 1, 0, 0, width}.Mul(m)
+		width, height = height, width
+	}
+	return m, width, height
+}

internal/codec/pdf/rendition.go

@@ -0,0 +1,158 @@
+// 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 pdf
+
+import (
+	"fmt"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// RenditionFloatingWindow 校验浮窗必需的像素尺寸，呈现偏好不写成视频固有尺寸
+// 入参: reader PDF阅读器, screen 媒体屏幕参数
+// 返回: bool 是否具备合法尺寸, error 引用错误
+func RenditionFloatingWindow(reader *pdfgo.Reader, screen pdfgo.Dictionary) (bool, error) {
+	value, err := reader.Resolve(screen["BE"])
+	if err != nil {
+		return false, err
+	}
+	preferences, _ := value.(pdfgo.Dictionary)
+	value, err = reader.Resolve(preferences["F"])
+	if err != nil {
+		return false, err
+	}
+	window, ok := value.(pdfgo.Dictionary)
+	if !ok {
+		return false, nil
+	}
+	value, err = reader.Resolve(window["D"])
+	if err != nil {
+		return false, err
+	}
+	size, ok := value.(pdfgo.Array)
+	if !ok || len(size) != 2 {
+		return false, nil
+	}
+	for _, part := range size {
+		value, err = reader.Resolve(part)
+		if err != nil {
+			return false, err
+		}
+		number, ok := value.(pdfgo.Integer)
+		if !ok || number < 0 {
+			return false, nil
+		}
+	}
+	return true, nil
+}
+
+// RenditionCriteria 检查媒体环境条件，未知尽力处理字段不影响候选可用性
+// 入参: reader PDF阅读器, rendition 媒体呈现或选择器
+// 返回: bool 是否可用, error 条件字典或引用错误
+func RenditionCriteria(reader *pdfgo.Reader, rendition *pdfgo.Rendition) (bool, error) {
+	for _, constraints := range []struct {
+		dict     pdfgo.Dictionary
+		required bool
+	}{{rendition.MustHonor, true}, {rendition.BestEffort, false}} {
+		for key, object := range constraints.dict {
+			if key != "C" {
+				if constraints.required {
+					return false, nil
+				}
+				continue
+			}
+			value, err := reader.Resolve(object)
+			if err != nil {
+				return false, err
+			}
+			criteria, ok := value.(pdfgo.Dictionary)
+			if !ok {
+				return false, fmt.Errorf("invalid media criteria")
+			}
+			for name, object := range criteria {
+				value, err := reader.Resolve(object)
+				if err != nil {
+					return false, err
+				}
+				if name == "Type" && value == pdfgo.Name("MediaCriteria") {
+					continue
+				}
+				switch name {
+				case "Type", "A", "C", "O", "S", "R", "D", "Z", "V", "P", "L":
+					return false, nil
+				default:
+					if constraints.required {
+						return false, nil
+					}
+				}
+			}
+		}
+	}
+	return true, nil
+}
+
+// RenditionParameters 合并可等价表达的播放参数，不支持的偏好不阻断播放
+// 入参: reader PDF阅读器, dict 参数字典, supported 字段及可表达值的检查
+// 返回: pdfgo.Dictionary 合并后的值, bool 是否可用, error 字典或引用错误
+func RenditionParameters(reader *pdfgo.Reader, dict pdfgo.Dictionary, supported map[pdfgo.Name]func(pdfgo.Object) bool) (pdfgo.Dictionary, bool, error) {
+	values := make(pdfgo.Dictionary)
+	for key := range dict {
+		if key != "Type" && key != "MH" && key != "BE" {
+			return nil, false, nil
+		}
+	}
+	value, err := reader.Resolve(dict["MH"])
+	if err != nil {
+		return nil, false, err
+	}
+	mandatory, _ := value.(pdfgo.Dictionary)
+	for _, key := range []pdfgo.Name{"BE", "MH"} {
+		value, err := reader.Resolve(dict[key])
+		if err != nil {
+			return nil, false, err
+		}
+		if value == nil {
+			continue
+		}
+		parameters, ok := value.(pdfgo.Dictionary)
+		if !ok {
+			return nil, false, fmt.Errorf("invalid media playback constraints")
+		}
+		for name, object := range parameters {
+			if _, overridden := mandatory[name]; key == "BE" && overridden {
+				continue
+			}
+			check := supported[name]
+			if check == nil {
+				if key == "MH" {
+					return nil, false, nil
+				}
+				continue
+			}
+			resolved, err := reader.Resolve(object)
+			if err != nil {
+				return nil, false, err
+			}
+			if !check(resolved) {
+				if key == "MH" {
+					return nil, false, nil
+				}
+				continue
+			}
+			values[name] = resolved
+		}
+	}
+	return values, true, nil
+}

internal/codec/pdf/shading.go

@@ -0,0 +1,96 @@
+// 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 pdf
+
+import (
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// ShadingColorants 复用原始浓度缓冲及原生通道映射，不跨并发采样共享
+type ShadingColorants struct {
+	paint   pdfgo.Paint
+	Process *pdfgo.ColorantProcess
+	tints   []float64
+	mesh    *pdfgo.MeshSampler
+}
+
+// ShadingColorantSpace 返回渐变的源色料定义，不使用备用颜色推断通道
+// 入参: paint 渐变画刷
+// 返回: *pdfgo.ColorantSpace 原始色料定义，普通渐变为nil
+func ShadingColorantSpace(paint pdfgo.Paint) *pdfgo.ColorantSpace {
+	switch {
+	case paint.Axial != nil:
+		return paint.Axial.ColorantSpace()
+	case paint.Radial != nil:
+		return paint.Radial.ColorantSpace()
+	case paint.Function != nil:
+		return paint.Function.ColorantSpace()
+	case paint.Mesh != nil:
+		return paint.Mesh.ColorantSpace()
+	}
+	return nil
+}
+
+// PrepareShadingColorants 为当前组建立原生过程采样，备用色保留原路径
+// 入参: paint 渐变画刷, space 组空间, softMask 是否用于软蒙版
+// 返回: *ShadingColorants 独立采样状态，不可原生映射时为nil
+func PrepareShadingColorants(paint pdfgo.Paint, space *pdfgo.ColorSpace, softMask bool) *ShadingColorants {
+	colorants := ShadingColorantSpace(paint)
+	Process := colorants.PrepareProcess(&pdfgo.ColorantDevice{Space: space}, space, softMask)
+	if Process == nil || Process.Mask() == ([4]bool{}) {
+		return nil
+	}
+	s := &ShadingColorants{paint: paint, Process: Process, tints: make([]float64, len(colorants.Names))}
+	if paint.Mesh != nil {
+		s.mesh = paint.Mesh.NewSampler()
+	}
+	return s
+}
+
+// At 在归一化位置求值轴向或径向原始浓度
+// 入参: position 归一化渐变参数
+// 返回: [4]float64 原生过程分量, error 求值错误
+func (s *ShadingColorants) At(position float64) ([4]float64, error) {
+	var err error
+	if s.paint.Axial != nil {
+		err = s.paint.Axial.ColorantValuesAt(position, s.tints)
+	} else {
+		err = s.paint.Radial.ColorantValuesAt(position, s.tints)
+	}
+	if err != nil {
+		return [4]float64{}, err
+	}
+	return s.Process.Convert(s.tints)
+}
+
+// PointAt 在函数定义域内求值原始浓度
+// 入参: point 函数坐标
+// 返回: [4]float64 原生过程分量, error 求值错误
+func (s *ShadingColorants) PointAt(point pdfgo.Point) ([4]float64, error) {
+	if err := s.paint.Function.ColorantValuesAt(point, s.tints); err != nil {
+		return [4]float64{}, err
+	}
+	return s.Process.Convert(s.tints)
+}
+
+// MeshAt 插值网格原始浓度并复用函数结果
+// 入参: patch 网格序号, u 横向参数, v 纵向参数
+// 返回: [4]float64 原生过程分量, error 求值错误
+func (s *ShadingColorants) MeshAt(patch int, u, v float64) ([4]float64, error) {
+	if err := s.mesh.ColorantValuesAt(patch, u, v, s.tints); err != nil {
+		return [4]float64{}, err
+	}
+	return s.Process.Convert(s.tints)
+}

internal/codec/pdf/threed.go

@@ -0,0 +1,270 @@
+// 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 pdf
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"image"
+	"math"
+
+	basethreed "github.com/xiaoqidun/ofdgo/internal/base/threed"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// ThreeDRenderOptions 控制PDF三维视口的静态绘制，不改变注解激活状态
+// 缓存与实例上限为0时采用basethreed.U3DRenderOptions的默认值
+// ResolveTexture按原始URL提供外部纹理，空值不访问外部资源
+// Nodes按名称替换PDF视图中的节点状态，可指定动作轨道与采样时间，不改变原始注解
+// Time以秒指定模型动画的采样时刻，零值为初始时刻
+type ThreeDRenderOptions struct {
+	Width, Height  int
+	MaxMemoryBytes int64
+	MaxInstances   int
+	ResolveTexture basethreed.U3DTextureResolver
+	Nodes          []basethreed.U3DNodeState
+	Time           float64
+}
+
+// RenderThreeD 按PDF相机、投影、背景与灯光绘制指定时刻的3DB区域，不执行脚本
+// 返回图像不含3DB以外的注解背景，未支持的视图效果返回明确错误
+// 每次从传入场景建立独立节点状态，不继承此前绘制的运行时状态
+// 入参: ctx 取消上下文, model 解码后的U3D模型, source PDF三维参数, options 输出与资源限制
+// 返回: *image.RGBA 不透明图像, error 参数、能力、预算或取消错误
+func RenderThreeD(ctx context.Context, model *basethreed.U3DModel, source pdfgo.ThreeD, options ThreeDRenderOptions) (*image.RGBA, error) {
+	if ctx == nil {
+		return nil, fmt.Errorf("invalid PDF 3D render context")
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if source.Format != "U3D" {
+		return nil, &pdfgo.UnsupportedError{Feature: "3D model format " + string(source.Format)}
+	}
+	if len(source.Measurements) != 0 {
+		return nil, &pdfgo.UnsupportedError{Feature: "3D view measurement rendering"}
+	}
+	presentation := source.Presentation
+	if presentation.Overlay != nil {
+		return nil, &pdfgo.UnsupportedError{Feature: "3D view overlay"}
+	}
+	if source.Background.RGB == nil {
+		return nil, &pdfgo.UnsupportedError{Feature: "3D background color space"}
+	}
+	box := source.ViewBox
+	width, height := box.XMax-box.XMin, box.YMax-box.YMin
+	if !finite(width) || !finite(height) || width <= 0 || height <= 0 {
+		return nil, fmt.Errorf("invalid PDF 3D viewport")
+	}
+	projection := pdfgo.ThreeDProjection{Subtype: "P", Clipping: "ANF", FieldOfView: 90, PerspectiveBinding: "W"}
+	if source.Projection != nil {
+		projection = *source.Projection
+	}
+	render := basethreed.U3DRenderOptions{Width: options.Width, Height: options.Height, MaxMemoryBytes: options.MaxMemoryBytes, MaxInstances: options.MaxInstances, Background: source.Background.RGB, ResolveTexture: options.ResolveTexture, Time: options.Time}
+	if err := threeDRenderMode(source, &render); err != nil {
+		return nil, err
+	}
+	if err := threeDNodeStates(ctx, presentation.Nodes, &render); err != nil {
+		return nil, err
+	}
+	if err := threeDSections(ctx, presentation.CrossSections, &render); err != nil {
+		return nil, err
+	}
+	r, err := basethreed.NewRenderer(ctx, model, render, options.Nodes)
+	if err != nil {
+		return nil, err
+	}
+	camera, view, err := threeDCamera(ctx, model, r, source.Camera)
+	if err != nil {
+		return nil, err
+	}
+	render.View = view
+	camera.ScaleX, camera.ScaleY, camera.Near = 1, 1, 1
+	render.Camera = &camera
+	passes, err := r.SelectView(render)
+	if err != nil {
+		return nil, err
+	}
+	if err := r.PrepareSections(render.Sections); err != nil {
+		return nil, err
+	}
+	scale, err := projection.ScaleFactor(source.ViewBox, source.AnnotationBox)
+	if err != nil {
+		return nil, err
+	}
+	camera.Perspective = projection.Subtype == "P"
+	camera.ScaleX = scale * float64(options.Width) / width
+	camera.ScaleY = scale * float64(options.Height) / height
+	switch projection.Clipping {
+	case "XNF":
+		camera.Near = 0
+		if projection.Near != nil {
+			camera.Near = *projection.Near
+		}
+		if !finite(camera.Near) || camera.Near < 0 || camera.Perspective && camera.Near == 0 {
+			return nil, fmt.Errorf("invalid PDF 3D near distance")
+		}
+		if projection.Far != nil {
+			camera.ClipFar = true
+			camera.Far = *projection.Far
+			if !finite(camera.Far) {
+				return nil, fmt.Errorf("invalid PDF 3D far distance")
+			}
+			if camera.Far < camera.Near {
+				passes, camera.Far = nil, 0
+				camera.ClipFar = false
+			}
+		}
+	case "ANF":
+		minimum, maximum, found, err := r.DepthRange()
+		if err != nil {
+			return nil, err
+		}
+		if !found {
+			passes = nil
+		}
+		camera.Near = minimum
+		if camera.Perspective {
+			if maximum <= 0 {
+				passes = nil
+			}
+			camera.Near = max(1e-300, maximum*1e-9)
+			if minimum > 0 {
+				camera.Near = max(1e-300, minimum/2)
+			}
+		}
+		camera.Far = math.Nextafter(maximum, math.Inf(1))
+		if !finite(camera.Far) || camera.Far <= camera.Near {
+			camera.Far = 0
+		}
+	default:
+		return nil, fmt.Errorf("invalid PDF 3D clipping style")
+	}
+	if _, err := r.SelectView(render); err != nil {
+		return nil, err
+	}
+	if source.Lighting.Subtype != "Artwork" && source.Lighting.Subtype != "" {
+		if err := r.Reserve(uint64(len(source.Lighting.Lights)), 56); err != nil {
+			return nil, err
+		}
+		render.Lighting = &basethreed.U3DLighting{DiffuseOffset: source.Lighting.Ambient, Lights: make([]basethreed.U3DDirectionalLight, len(source.Lighting.Lights))}
+		for i, light := range source.Lighting.Lights {
+			if i%256 == 0 {
+				if err := ctx.Err(); err != nil {
+					return nil, err
+				}
+			}
+			direction := light.Direction
+			if light.CameraAttached {
+				direction = [3]float64{0, 0, 1}
+			}
+			render.Lighting.Lights[i] = basethreed.U3DDirectionalLight{Color: light.Color, Direction: direction, CameraRelative: light.CameraAttached}
+		}
+	}
+	return r.Render(render, passes)
+}
+
+// threeDCamera 解析PDF相机来源并保留模型视图的绘制轮次
+// 入参: ctx 取消上下文, model 三维模型, renderer 场景实例, source 相机来源
+// 返回: basethreed.U3DCamera 相机变换, string 视图节点, error 路径或变换错误
+func threeDCamera(ctx context.Context, model *basethreed.U3DModel, renderer *basethreed.Renderer, source pdfgo.ThreeDCamera) (basethreed.U3DCamera, string, error) {
+	var camera basethreed.U3DCamera
+	selected := -1
+	for i, node := range model.Nodes {
+		if i%256 == 0 {
+			if err := ctx.Err(); err != nil {
+				return camera, "", err
+			}
+		}
+		if node.Kind == "View" {
+			selected = i
+			break
+		}
+	}
+	if source.Source == "M" {
+		m := source.Matrix
+		camera.ToWorld = [16]float64{m[0], m[1], m[2], 0, m[3], m[4], m[5], 0, m[6], m[7], m[8], 0, m[9], m[10], m[11], 1}
+	} else {
+		if source.Source != "" && source.Source != "U3D" || source.Source == "U3D" && len(source.Path) == 0 {
+			return camera, "", fmt.Errorf("invalid PDF 3D camera source")
+		}
+		if source.Source == "U3D" {
+			selected = -1
+			for i, node := range model.Nodes {
+				if i%256 == 0 {
+					if err := ctx.Err(); err != nil {
+						return camera, "", err
+					}
+				}
+				if node.Name == source.Path[len(source.Path)-1] {
+					selected = i
+					break
+				}
+			}
+		}
+		if selected < 0 || model.Nodes[selected].Kind != "View" {
+			return camera, "", fmt.Errorf("missing PDF 3D camera node")
+		}
+		var err error
+		camera.ToWorld, err = renderer.ViewCamera(selected, source.Path, source.Source == "U3D")
+		if errors.Is(err, basethreed.ErrAmbiguousCamera) {
+			return camera, "", &pdfgo.UnsupportedError{Feature: "ambiguous 3D camera instance"}
+		}
+		if errors.Is(err, basethreed.ErrCameraNotFound) {
+			return camera, "", fmt.Errorf("missing PDF 3D camera path")
+		}
+		if err != nil {
+			return camera, "", err
+		}
+	}
+	view := ""
+	if selected >= 0 {
+		view = model.Nodes[selected].Name
+	}
+	return camera, view, nil
+}
+
+// threeDNodeStates 将PDF节点参数转为场景覆盖，转换缓存计入绘制预算
+// 入参: ctx 取消上下文, nodes 节点参数, options 绘制选项
+// 返回: error 预算或取消错误
+func threeDNodeStates(ctx context.Context, nodes []pdfgo.ThreeDNode, options *basethreed.U3DRenderOptions) error {
+	if len(nodes) == 0 {
+		return nil
+	}
+	limit := options.MaxMemoryBytes
+	if limit == 0 {
+		limit = basethreed.DefaultBytes
+	}
+	if limit <= 0 || uint64(len(nodes)) >= uint64(limit)/168 {
+		return fmt.Errorf("PDF 3D node memory exceeds limit")
+	}
+	options.MaxMemoryBytes = limit - int64(len(nodes))*168
+	options.Nodes = make([]basethreed.U3DNodeState, len(nodes))
+	for i, node := range nodes {
+		if i%256 == 0 {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+		}
+		state := basethreed.U3DNodeState{Name: node.Name, Opacity: node.Opacity, Visible: node.Visible}
+		if node.Matrix != nil {
+			m := node.Matrix
+			state.Matrix = &[16]float64{m[0], m[1], m[2], 0, m[3], m[4], m[5], 0, m[6], m[7], m[8], 0, m[9], m[10], m[11], 1}
+		}
+		options.Nodes[i] = state
+	}
+	return nil
+}

internal/codec/pdf/threed_mode.go

@@ -0,0 +1,77 @@
+// 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 pdf
+
+import (
+	basethreed "github.com/xiaoqidun/ofdgo/internal/base/threed"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// threeDRenderMode 将PDF标准绘制模式映射到通用几何绘制参数
+// 入参: source 三维参数, options 绘制选项
+// 返回: error 未支持的模式错误
+func threeDRenderMode(source pdfgo.ThreeD, options *basethreed.U3DRenderOptions) error {
+	mode := source.Presentation.RenderMode
+	if mode == nil {
+		return nil
+	}
+	switch mode.Subtype {
+	case "Solid":
+	case "Transparent":
+		options.Opacity = &mode.Opacity
+	case "SolidWireframe", "TransparentWireframe":
+		options.Mode, options.AuxiliaryColor = basethreed.U3DRenderSolidWireframe, &mode.AuxiliaryColor
+		if mode.Subtype == "TransparentWireframe" {
+			options.Opacity = &mode.Opacity
+		}
+	case "Wireframe":
+		options.Mode, options.AuxiliaryColor = basethreed.U3DRenderWireframe, &mode.AuxiliaryColor
+	case "ShadedWireframe":
+		options.Mode = basethreed.U3DRenderShadedWireframe
+	case "HiddenWireframe":
+		options.Mode, options.AuxiliaryColor = basethreed.U3DRenderHiddenWireframe, &mode.AuxiliaryColor
+	case "Vertices":
+		options.Mode, options.AuxiliaryColor = basethreed.U3DRenderVertices, &mode.AuxiliaryColor
+	case "ShadedVertices":
+		options.Mode = basethreed.U3DRenderShadedVertices
+	case "BoundingBox":
+		options.Mode, options.AuxiliaryColor = basethreed.U3DRenderBoundingBox, &mode.AuxiliaryColor
+	case "TransparentBoundingBox", "TransparentBoundingBoxOutline":
+		options.Mode = basethreed.U3DRenderBoundingBoxFaces
+		options.FaceColor, options.Opacity = mode.FaceColor, &mode.Opacity
+		if mode.Subtype == "TransparentBoundingBoxOutline" {
+			options.Mode, options.AuxiliaryColor = basethreed.U3DRenderBoundingBoxOutline, &mode.AuxiliaryColor
+		}
+	case "Illustration":
+		options.Mode = basethreed.U3DRenderIllustration
+		options.AuxiliaryColor, options.FaceColor, options.CreaseAngle = &mode.AuxiliaryColor, mode.FaceColor, &mode.CreaseAngle
+	case "SolidOutline", "ShadedIllustration":
+		options.Mode = basethreed.U3DRenderSolidOutline
+		if mode.Subtype == "ShadedIllustration" {
+			options.Mode = basethreed.U3DRenderShadedIllustration
+		}
+		options.AuxiliaryColor, options.CreaseAngle = &mode.AuxiliaryColor, &mode.CreaseAngle
+	default:
+		return &pdfgo.UnsupportedError{Feature: "3D render mode " + string(mode.Subtype)}
+	}
+	if mode.AnnotationBackground && (mode.Subtype == "Illustration" || mode.Subtype == "TransparentBoundingBox" || mode.Subtype == "TransparentBoundingBoxOutline") {
+		options.FaceColor = source.AnnotationBackground
+		if source.AnnotationBackground == nil {
+			zero := 0.0
+			options.Opacity = &zero
+		}
+	}
+	return nil
+}

internal/codec/pdf/threed_section.go

@@ -0,0 +1,71 @@
+// 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 pdf
+
+import (
+	"context"
+	"fmt"
+	"math"
+
+	basethreed "github.com/xiaoqidun/ofdgo/internal/base/threed"
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// threeDSections 按XYZ顺序构造剖切方向，中心保持为世界坐标固定点
+// 入参: ctx 取消上下文, sections PDF剖切面, options 绘制选项
+// 返回: error 方向、预算或取消错误
+func threeDSections(ctx context.Context, sections []pdfgo.ThreeDCrossSection, options *basethreed.U3DRenderOptions) error {
+	if len(sections) == 0 {
+		return nil
+	}
+	limit := options.MaxMemoryBytes
+	if limit == 0 {
+		limit = basethreed.DefaultBytes
+	}
+	if limit <= 0 || uint64(len(sections)) >= uint64(limit)/136 {
+		return fmt.Errorf("PDF 3D section memory exceeds limit")
+	}
+	options.MaxMemoryBytes = limit - int64(len(sections))*136
+	options.Sections = make([]basethreed.U3DCrossSection, len(sections))
+	for i, source := range sections {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		if source.Axis < 0 || source.Axis > 2 {
+			return fmt.Errorf("invalid PDF 3D section axis")
+		}
+		section := basethreed.U3DCrossSection{Center: source.Center, Color: source.Color, Opacity: source.Opacity}
+		section.AxisU[(source.Axis+1)%3], section.AxisV[(source.Axis+2)%3] = 1, 1
+		for axis, angle := range source.Rotation {
+			if axis == source.Axis {
+				continue
+			}
+			if !finite(angle) {
+				return fmt.Errorf("invalid PDF 3D section rotation")
+			}
+			sin, cos := math.Sincos(math.Remainder(angle, 360) * math.Pi / 180)
+			a, b := (axis+1)%3, (axis+2)%3
+			for _, vector := range []*[3]float64{&section.AxisU, &section.AxisV} {
+				vector[a], vector[b] = cos*vector[a]-sin*vector[b], sin*vector[a]+cos*vector[b]
+			}
+		}
+		if source.IntersectionVisible {
+			color := source.IntersectionColor
+			section.Intersection = &color
+		}
+		options.Sections[i] = section
+	}
+	return nil
+}