mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 08:46:55 +08:00
343 lines
11 KiB
Go
343 lines
11 KiB
Go
// 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 os2 := basefont.NormalizeOS2(tables["OS/2"]); len(os2) != len(tables["OS/2"]) {
|
|
tables["OS/2"] = os2
|
|
changed = true
|
|
}
|
|
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
|
|
}
|