diff --git a/internal/base/font/sfnt.go b/internal/base/font/sfnt.go
index 1cfb680..11cf5ff 100644
--- a/internal/base/font/sfnt.go
+++ b/internal/base/font/sfnt.go
@@ -18,7 +18,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"maps"
-	"sort"
+	"slices"
 	"sync"
 
 	"github.com/go-text/typesetting/font/opentype/tables"
@@ -34,10 +34,11 @@ type SFNT struct {
 	reverse                            map[uint16][]rune
 }
 
-// sfntCmap 保存编码记录及对应字符映射
+// sfntCmap 保存编码记录及对应字符映射，标记已解析的共享子表
 type sfntCmap struct {
 	platform, encoding, format uint16
 	mapping                    map[rune]uint16
+	duplicate                  bool
 }
 
 // ParseSFNT 校验独立字体的必需表、度量范围及字符映射
@@ -86,6 +87,9 @@ func ParseSFNTTables(table map[string][]byte) (*SFNT, error) {
 	}
 	f.cmaps = cmaps
 	for _, cmap := range f.cmaps {
+		if cmap.duplicate {
+			continue
+		}
 		for _, glyph := range cmap.mapping {
 			if glyph >= f.count {
 				return nil, fmt.Errorf("cmap glyph index out of range")
@@ -150,7 +154,7 @@ func readSFNTCmaps(data []byte) ([]sfntCmap, error) {
 			}
 			parsed[offset] = mapping
 		}
-		result = append(result, sfntCmap{binary.BigEndian.Uint16(record), binary.BigEndian.Uint16(record[2:]), format, mapping})
+		result = append(result, sfntCmap{platform: binary.BigEndian.Uint16(record), encoding: binary.BigEndian.Uint16(record[2:]), format: format, mapping: mapping, duplicate: found})
 	}
 	return result, nil
 }
@@ -164,11 +168,11 @@ func (f *SFNT) UnitsPerEm() uint16 { return f.units }
 func (f *SFNT) NumGlyphs() uint16 { return f.count }
 
 // CmapEntries 返回各编码记录的映射项总数，共享子表按记录分别计数
-// 返回: int 用于缓存预算的映射项数量
-func (f *SFNT) CmapEntries() int {
-	count := 0
+// 返回: uint64 用于缓存预算的映射项数量
+func (f *SFNT) CmapEntries() uint64 {
+	var count uint64
 	for _, cmap := range f.cmaps {
-		count += len(cmap.mapping)
+		count += uint64(len(cmap.mapping))
 	}
 	return count
 }
@@ -178,6 +182,9 @@ func (f *SFNT) CmapEntries() int {
 // 返回: uint16 字形编号
 func (f *SFNT) GlyphIndex(char rune) uint16 {
 	for _, cmap := range f.cmaps {
+		if cmap.duplicate {
+			continue
+		}
 		if gid := cmap.mapping[char]; gid != 0 {
 			return gid
 		}
@@ -193,6 +200,9 @@ func (f *SFNT) glyphCharacters(gid uint16) []rune {
 		f.reverse = make(map[uint16][]rune)
 		seen := make(map[rune]bool)
 		for _, cmap := range f.cmaps {
+			if cmap.duplicate {
+				continue
+			}
 			for char, glyph := range cmap.mapping {
 				if glyph != 0 && !seen[char] {
 					f.reverse[glyph] = append(f.reverse[glyph], char)
@@ -201,7 +211,7 @@ func (f *SFNT) glyphCharacters(gid uint16) []rune {
 			}
 		}
 		for _, chars := range f.reverse {
-			sort.Slice(chars, func(i, j int) bool { return chars[i] < chars[j] })
+			slices.Sort(chars)
 		}
 	})
 	return f.reverse[gid]
diff --git a/internal/base/font/subset.go b/internal/base/font/subset.go
index 9763ce8..301bd57 100644
--- a/internal/base/font/subset.go
+++ b/internal/base/font/subset.go
@@ -134,7 +134,8 @@ func SubsetSFNT(data []byte, glyphs []uint16, mapped bool) ([]byte, error) {
 		if err != nil {
 			return nil, err
 		}
-		if subset := SubsetSourceSFNT(fixed, usage); subset != nil {
+		sfnt.Tables = tables
+		if subset := subsetSourceSFNT(sfnt, usage, len(fixed)); subset != nil {
 			return subset, nil
 		}
 		return fixed, nil
@@ -147,7 +148,7 @@ func SubsetSFNT(data []byte, glyphs []uint16, mapped bool) ([]byte, error) {
 // 入参: data 字体数据, usage 全包用字记录
 // 返回: []byte 更小的字体子集，无确定收益时为空
 func SubsetSourceSFNT(data []byte, usage *Usage) []byte {
-	if usage.Unsafe || len(usage.Characters)+len(usage.Glyphs) == 0 || bytes.HasPrefix(data, []byte("ttcf")) {
+	if usage == nil || usage.Unsafe || len(usage.Characters)+len(usage.Glyphs) == 0 || bytes.HasPrefix(data, []byte("ttcf")) {
 		return nil
 	}
 	fontTables, err := FileTables(data, 0)
@@ -162,7 +163,17 @@ func SubsetSourceSFNT(data []byte, usage *Usage) []byte {
 		}
 	}
 	sfnt, err := ParseSFNTTables(fontTables)
-	if err != nil || !sfnt.IsTrueType && !sfnt.IsCFF || fontEmbeddingFlags(sfnt)&0x0100 != 0 {
+	if err != nil {
+		return nil
+	}
+	return subsetSourceSFNT(sfnt, usage, len(data))
+}
+
+// subsetSourceSFNT 复用已校验的字体表裁剪字形，仅返回小于原编码的结果
+// 入参: sfnt 已解析字体, usage 用字记录, size 原编码长度
+// 返回: []byte 更小的字体子集，无确定收益时为空
+func subsetSourceSFNT(sfnt *SFNT, usage *Usage, size int) []byte {
+	if usage == nil || usage.Unsafe || len(usage.Characters)+len(usage.Glyphs) == 0 || !sfnt.IsTrueType && !sfnt.IsCFF || fontEmbeddingFlags(sfnt)&0x0100 != 0 {
 		return nil
 	}
 	var unicodeTables []sfntCmap
@@ -178,6 +189,9 @@ func SubsetSourceSFNT(data []byte, usage *Usage) []byte {
 		return nil
 	}
 	glyphs := maps.Clone(usage.Glyphs)
+	if glyphs == nil {
+		glyphs = make(map[uint16]bool)
+	}
 	glyphs[0] = true
 	mapping := make(map[rune]uint16, len(usage.Characters))
 	for char := range usage.Characters {
@@ -210,7 +224,7 @@ func SubsetSourceSFNT(data []byte, usage *Usage) []byte {
 		tables["cmap"] = buildCmapWithVariations(sfnt.NumGlyphs(), mapping, variations)
 		delete(tables, "DSIG")
 		result, err := SerializeOTF(tables)
-		if err != nil || len(result) >= len(data) {
+		if err != nil || len(result) >= size {
 			return nil
 		}
 		return result
@@ -258,7 +272,7 @@ func SubsetSourceSFNT(data []byte, usage *Usage) []byte {
 	clear(tables["head"][8:12])
 	delete(tables, "DSIG")
 	result, err := SerializeOTF(tables)
-	if err != nil || len(result) >= len(data) {
+	if err != nil || len(result) >= size {
 		return nil
 	}
 	return result
diff --git a/internal/base/image/scale.go b/internal/base/image/scale.go
index 7d48e90..f395084 100644
--- a/internal/base/image/scale.go
+++ b/internal/base/image/scale.go
@@ -147,6 +147,7 @@ func rasterImageAxis(first, end, source, limit int, scale, offset float64) []ras
 	result := make([]rasterAxisSample, 0, end-first)
 	argument := math.Min(1, math.Abs(scale))
 	support := draw.CatmullRom.Support / argument
+	count := 0
 	for pixel := first; pixel < end; pixel++ {
 		center := (float64(pixel) + .5 - offset) / scale
 		if center < float64(source) || center >= float64(limit) {
@@ -155,7 +156,18 @@ func rasterImageAxis(first, end, source, limit int, scale, offset float64) []ras
 		center -= .5
 		start := int(max(float64(source), math.Floor(center-support)))
 		stop := int(min(float64(limit), math.Ceil(center+support)))
-		weights := make([]float64, stop-start)
+		count += stop - start
+		result = append(result, rasterAxisSample{pixel: pixel, first: start})
+	}
+	buffer := make([]float64, count)
+	for index := range result {
+		sample := &result[index]
+		center := (float64(sample.pixel)+.5-offset)/scale - .5
+		start := sample.first
+		stop := int(min(float64(limit), math.Ceil(center+support)))
+		n := stop - start
+		weights := buffer[:n:n]
+		buffer = buffer[n:]
 		total := 0.0
 		for i := range weights {
 			distance := math.Abs((float64(start+i) - center) * argument)
@@ -167,7 +179,7 @@ func rasterImageAxis(first, end, source, limit int, scale, offset float64) []ras
 		for i := range weights {
 			weights[i] /= total
 		}
-		result = append(result, rasterAxisSample{pixel: pixel, first: start, weights: weights})
+		sample.weights = weights
 	}
 	return result
 }
diff --git a/ofdgo_compression_resources.go b/ofdgo_compression_resources.go
index da5ae30..78bda7a 100644
--- a/ofdgo_compression_resources.go
+++ b/ofdgo_compression_resources.go
@@ -194,6 +194,7 @@ func (e *Editor) compressResourceReferences(parts map[string][]byte, reader *Rea
 	formats := make(map[string]string)
 	seen := make(map[resourceScope]map[[32]byte]string)
 	imageResults := make(map[outputImageKey][]byte)
+	imageDigests := make(map[outputImageKey][32]byte)
 	imageSources := make(map[string]outputImageSource)
 	ordered := slices.Sorted(maps.Keys(actual))
 	sizes := make(map[string]uint64, len(files))
@@ -307,7 +308,12 @@ func (e *Editor) compressResourceReferences(parts map[string][]byte, reader *Rea
 				if candidate != nil {
 					data = candidate
 					parts[actual[key]] = data
-					source.key.hash = sha256.Sum256(data)
+					digest, ok := imageDigests[cacheKey]
+					if !ok {
+						digest = sha256.Sum256(data)
+						imageDigests[cacheKey] = digest
+					}
+					source.key.hash = digest
 				}
 				if data != nil {
 					source.format = outputImageFormat(data)
diff --git a/ofdgo_renderer_font_canvas.go b/ofdgo_renderer_font_canvas.go
index b2c83d8..7867979 100644
--- a/ofdgo_renderer_font_canvas.go
+++ b/ofdgo_renderer_font_canvas.go
@@ -214,7 +214,7 @@ func (r *Renderer) cachedTextGlyphPath(face *canvas.FontFace, glyph textGlyph) (
 			for _, data := range metrics.Tables {
 				cost += uint64(len(data)) * 8
 			}
-			cost += uint64(metrics.CmapEntries()) * 48
+			cost += metrics.CmapEntries() * 48
 			cache.put(face.Font, outlines, int(min(cost, uint64(cache.limit)+1)))
 		}
 		r.canvasState().fontOutlines[face.Font] = outlines
diff --git a/ofdgo_renderer_pdf_canvas.go b/ofdgo_renderer_pdf_canvas.go
index 270dc42..4af0083 100644
--- a/ofdgo_renderer_pdf_canvas.go
+++ b/ofdgo_renderer_pdf_canvas.go
@@ -34,6 +34,7 @@ type pdfRenderer struct {
 	*pdf.PDF
 	glyphPaths  renderCache[*canvas.Path, *canvas.Path]
 	fonts       map[*canvas.Font]*canvas.Font
+	cffFonts    map[*canvas.Font][]*pdfFontSubset
 	images      [][]image.Image
 	exactImages bool
 	imageError  error
diff --git a/ofdgo_renderer_pdf_text.go b/ofdgo_renderer_pdf_text.go
index 27952e1..01c2053 100644
--- a/ofdgo_renderer_pdf_text.go
+++ b/ofdgo_renderer_pdf_text.go
@@ -15,6 +15,9 @@
 package ofdgo
 
 import (
+	"fmt"
+	"slices"
+
 	"github.com/tdewolff/canvas"
 	canvastext "github.com/tdewolff/canvas/text"
 	basefont "github.com/xiaoqidun/ofdgo/internal/base/font"
@@ -22,6 +25,12 @@ import (
 	"github.com/xiaoqidun/pdfgo"
 )
 
+// pdfFontSubset 保存独立CFF输出字体及实际用字，包含缺省字形
+type pdfFontSubset struct {
+	font   *canvas.Font
+	glyphs map[uint16]bool
+}
+
 // RenderText 记录后端文字区段，写出时校验数量并关联原文
 // 入参: text 画布文字, matrix 文字变换
 func (r *pdfRenderer) RenderText(text *canvas.Text, matrix canvas.Matrix) {
@@ -68,18 +77,89 @@ func (r *pdfRenderer) glyphText(face *canvas.FontFace, glyph textGlyph) (*canvas
 	outputFace := *face
 	outputFace.Font = font
 	face = &outputFace
+	var text *canvas.Text
 	if glyph.GlyphID < 0 || glyph.GlyphID > 0xffff {
-		return canvas.NewTextLine(face, glyph.Text, canvas.Left), nil
+		text = canvas.NewTextLine(face, glyph.Text, canvas.Left)
+	} else {
+		id := uint16(glyph.GlyphID)
+		text = canvas.NewTextLine(face, " ", canvas.Left)
+		text.WalkLines(func(_ float64, spans []canvas.TextSpan) {
+			for i := range spans {
+				spans[i].Text = glyph.Text
+				spans[i].Glyphs = []canvastext.Glyph{{SFNT: face.Font.SFNT, Size: face.Size, ID: id, XAdvance: int32(face.Font.GlyphAdvance(id)), Text: glyph.Text}}
+			}
+		})
 	}
-	id := uint16(glyph.GlyphID)
-	text := canvas.NewTextLine(face, " ", canvas.Left)
-	text.WalkLines(func(_ float64, spans []canvas.TextSpan) {
-		for i := range spans {
-			spans[i].Text = glyph.Text
-			spans[i].Glyphs = []canvastext.Glyph{{SFNT: face.Font.SFNT, Size: face.Size, ID: id, XAdvance: int32(face.Font.GlyphAdvance(id)), Text: glyph.Text}}
+	if font.IsCFF {
+		if err := r.cffTextFont(font, text); err != nil {
+			return nil, err
+		}
+	}
+	return text, nil
+}
+
+// cffTextFont 按实际用字隔离CFF子集，避免后端清除字形名后超出ISOAdobe字符集容量
+// 入参: font 独立输出字体, text 已定位文字
+// 返回: error 字形数量或字体解析错误
+func (r *pdfRenderer) cffTextFont(font *canvas.Font, text *canvas.Text) error {
+	const limit = 229
+	ids := []uint16{0}
+	text.WalkSpans(func(_, _ float64, span canvas.TextSpan) {
+		for _, glyph := range span.Glyphs {
+			if !slices.Contains(ids, glyph.ID) {
+				ids = append(ids, glyph.ID)
+			}
 		}
 	})
-	return text, nil
+	if len(ids) > limit {
+		return fmt.Errorf("CFF text glyph count exceeds output subset capacity")
+	}
+	var selected *pdfFontSubset
+	for _, subset := range r.cffFonts[font] {
+		count := len(subset.glyphs)
+		for _, id := range ids {
+			if !subset.glyphs[id] {
+				count++
+			}
+		}
+		if count <= limit {
+			selected = subset
+			break
+		}
+	}
+	if selected == nil {
+		output := font
+		if len(r.cffFonts[font]) != 0 {
+			loaded, err := loadCanvasFont(basefont.SFNTData(font.Tables), 0, font.Style())
+			if err != nil {
+				return err
+			}
+			copy := *font
+			copy.SFNT = loaded.SFNT
+			output = &copy
+		}
+		selected = &pdfFontSubset{font: output, glyphs: make(map[uint16]bool)}
+		if r.cffFonts == nil {
+			r.cffFonts = make(map[*canvas.Font][]*pdfFontSubset)
+		}
+		r.cffFonts[font] = append(r.cffFonts[font], selected)
+	}
+	for _, id := range ids {
+		selected.glyphs[id] = true
+	}
+	if selected.font != font {
+		text.WalkLines(func(_ float64, spans []canvas.TextSpan) {
+			for i := range spans {
+				face := *spans[i].Face
+				face.Font = selected.font
+				spans[i].Face = &face
+				for j := range spans[i].Glyphs {
+					spans[i].Glyphs[j].SFNT = selected.font.SFNT
+				}
+			}
+		})
+	}
+	return nil
 }
 
 // pdfTextSupported 核对原生文字的字形和未裁剪范围，复用实际绘制的字形缓存