mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
450 lines
16 KiB
Go
450 lines
16 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package font
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"math"
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"sort"
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)
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// finite 判断数值是否有限
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// 入参: value 数值
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// 返回: bool 是否有限
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func finite(value float64) bool {
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return !math.IsNaN(value) && !math.IsInf(value, 0)
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}
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// ExtractCollectionFont 提取集合中的单个OpenType字体，保留表内容并重新计算校验和
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// 入参: data 集合数据, index 字体索引
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// 返回: []byte 单字体数据, error 错误信息
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func ExtractCollectionFont(data []byte, index int) ([]byte, error) {
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tables, err := FileTables(data, index)
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if err != nil {
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return nil, err
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}
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if len(tables["head"]) < 12 {
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return nil, fmt.Errorf("invalid head font table")
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}
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return SerializeOTF(tables)
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}
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// FileTables 读取单字体或集合指定项的表目录，不复制表数据
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// 入参: data 字体数据, index 字体索引
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// 返回: map[string][]byte 字体表, error 错误信息
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func FileTables(data []byte, index int) (map[string][]byte, error) {
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count, err := FileCount(data)
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if err != nil {
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return nil, err
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}
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if index < 0 || index >= count {
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return nil, fmt.Errorf("invalid font index %d", index)
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}
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var offset uint64
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if string(data[:4]) == "ttcf" {
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offset = uint64(binary.BigEndian.Uint32(data[12+index*4:]))
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}
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if offset > uint64(len(data)-12) {
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return nil, fmt.Errorf("invalid font offset")
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}
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header := data[offset : offset+12]
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if string(header[:4]) != "\x00\x01\x00\x00" && string(header[:4]) != "OTTO" && string(header[:4]) != "true" {
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return nil, fmt.Errorf("invalid OpenType header")
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}
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tableCount := uint64(binary.BigEndian.Uint16(header[4:]))
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offset += 12
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if tableCount == 0 || tableCount > (uint64(len(data))-offset)/16 {
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return nil, fmt.Errorf("invalid font table directory")
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}
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tables := make(map[string][]byte, tableCount)
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for i := uint64(0); i < tableCount; i++ {
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entry := data[offset+i*16 : offset+(i+1)*16]
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tag := string(entry[:4])
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start := uint64(binary.BigEndian.Uint32(entry[8:]))
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length := uint64(binary.BigEndian.Uint32(entry[12:]))
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if start > uint64(len(data)) || length > uint64(len(data))-start {
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return nil, fmt.Errorf("invalid %s font table range", tag)
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}
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if _, exists := tables[tag]; exists {
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return nil, fmt.Errorf("duplicate %s font table", tag)
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}
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tables[tag] = data[start : start+length]
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}
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return tables, nil
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}
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// NormalizePDFProgram 修复可确定的PDF内嵌SFNT封装，不补造TrueType轮廓或字形编号
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// 入参: data 原始字体程序
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// 返回: []byte 原程序或独立修复程序, bool 是否修复, error 无法确认的目录或度量错误
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func NormalizePDFProgram(data []byte) ([]byte, bool, error) {
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if len(data) < 12 || string(data[:4]) != "OTTO" && string(data[:4]) != "\x00\x01\x00\x00" && string(data[:4]) != "true" {
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return data, false, nil
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}
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count := int(binary.BigEndian.Uint16(data[4:6]))
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if count == 0 || count > (len(data)-12)/16 {
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return nil, false, fmt.Errorf("unrecoverable PDF font directory size")
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}
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first := len(data)
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for n := 0; n < count; n++ {
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record := data[12+n*16:]
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start, size := uint64(binary.BigEndian.Uint32(record[8:])), uint64(binary.BigEndian.Uint32(record[12:]))
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if size != 0 && start >= 12 && start+size <= uint64(len(data)) {
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first = min(first, int(start))
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}
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}
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changed := false
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if first < 12+count*16 {
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if (first-12)%16 != 0 {
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return nil, false, fmt.Errorf("ambiguous PDF font directory overlap")
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}
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actual := (first - 12) / 16
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for n := 0; n < count; n++ {
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record := data[12+n*16:]
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printable := true
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for _, b := range record[:4] {
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printable = printable && b >= 32 && b <= 126
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}
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if printable != (n < actual) {
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return nil, false, fmt.Errorf("ambiguous PDF font table count")
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}
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if n < actual {
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start, size := uint64(binary.BigEndian.Uint32(record[8:])), uint64(binary.BigEndian.Uint32(record[12:]))
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if size != 0 && (start < uint64(first) || start+size > uint64(len(data))) {
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return nil, false, fmt.Errorf("incomplete PDF font table")
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}
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}
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}
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data = bytes.Clone(data)
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binary.BigEndian.PutUint16(data[4:6], uint16(actual))
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changed = true
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}
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tables, err := FileTables(data, 0)
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if err != nil {
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return nil, false, err
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}
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if head := tables["head"]; len(head) > 54 && len(head) <= 57 {
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tables["head"] = head[:54]
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changed = true
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}
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if hhea := tables["hhea"]; len(hhea) > 36 && len(hhea) <= 39 && binary.BigEndian.Uint32(hhea) == 0x00010000 {
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tables["hhea"] = hhea[:36]
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changed = true
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}
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if maxp := tables["maxp"]; tables["glyf"] != nil && len(maxp) > 32 && len(maxp) <= 35 && binary.BigEndian.Uint32(maxp) == 0x00010000 {
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tables["maxp"] = maxp[:32]
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changed = true
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}
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if post := tables["post"]; len(post) > 32 && binary.BigEndian.Uint32(post) == 0x00030000 {
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tables["post"] = post[:32]
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changed = true
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}
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if cvt := tables["cvt "]; len(cvt)%2 != 0 && cvt[len(cvt)-1] == 0 {
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tables["cvt "] = cvt[:len(cvt)-1]
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changed = true
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}
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if len(tables["CFF "]) != 0 && len(tables["head"]) == 0 && len(tables["maxp"]) == 0 && len(tables["hhea"]) == 0 && len(tables["hmtx"]) == 0 {
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program, _, err := WrapCFFToOTF(tables["CFF "])
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return program, true, err
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}
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if maxp := tables["maxp"]; len(tables["CFF "]) != 0 && tables["glyf"] == nil && len(maxp) >= 6 && (binary.BigEndian.Uint32(maxp) == 0x00010000 || binary.BigEndian.Uint32(maxp) == 0x00005000 && len(maxp) != 6) {
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count, err := parseCFFAndCountGlyphs(tables["CFF "])
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if err != nil {
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return nil, false, err
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}
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if count != int(binary.BigEndian.Uint16(maxp[4:6])) {
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program, _, err := WrapCFFToOTF(tables["CFF "])
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if err != nil {
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return nil, false, err
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}
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rebuilt, err := FileTables(program, 0)
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if err != nil {
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return nil, false, err
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}
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if len(tables["head"]) < 20 || !bytes.Equal(tables["head"][18:20], rebuilt["head"][18:20]) {
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return nil, false, fmt.Errorf("CFF and SFNT design units differ")
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}
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return program, true, nil
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}
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tables["maxp"] = buildCFFMaxpTable(uint16(count))
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changed = true
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}
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if !changed {
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return data, false, nil
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}
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program, err := SerializeOTF(tables)
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return program, true, err
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}
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// calcTableChecksum 计算字体表校验和
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// 入参: data 表数据
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// 返回: uint32 校验和
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func calcTableChecksum(data []byte) uint32 {
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var a, b, c, d uint32
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for len(data) >= 16 {
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a += binary.BigEndian.Uint32(data[:4])
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b += binary.BigEndian.Uint32(data[4:8])
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c += binary.BigEndian.Uint32(data[8:12])
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d += binary.BigEndian.Uint32(data[12:16])
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data = data[16:]
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}
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sum := a + b + c + d
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for len(data) >= 4 {
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sum += binary.BigEndian.Uint32(data[:4])
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data = data[4:]
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}
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for i, value := range data {
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sum += uint32(value) << (24 - 8*i)
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}
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return sum
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}
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// buildHeadTable 构建head表
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// 入参: unitsPerEm 每em单位数
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// 返回: []byte head表数据
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func buildHeadTable(unitsPerEm uint16) []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint16(1))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0x5F0F3CF5))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, unitsPerEm)
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binary.Write(buf, binary.BigEndian, int64(0))
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binary.Write(buf, binary.BigEndian, int64(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(-500))
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binary.Write(buf, binary.BigEndian, int16(1000))
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binary.Write(buf, binary.BigEndian, int16(1000))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, int16(2))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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return buf.Bytes()
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}
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// buildHheaTable 构建hhea表
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// 入参: numGlyphs 字形数量
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// 返回: []byte hhea表数据
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func buildHheaTable(numGlyphs uint16) []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint16(1))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, int16(800))
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binary.Write(buf, binary.BigEndian, int16(-200))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, uint16(1000))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(1000))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, uint16(numGlyphs))
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return buf.Bytes()
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}
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// buildCFFMaxpTable 构建CFF轮廓使用的maxp 0.5表
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// 入参: numGlyphs 字形数量
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// 返回: []byte maxp表数据
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func buildCFFMaxpTable(numGlyphs uint16) []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint32(0x00005000))
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binary.Write(buf, binary.BigEndian, uint16(numGlyphs))
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return buf.Bytes()
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}
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// buildTrueTypeMaxpTable 构建TrueType轮廓使用的maxp 1.0表
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// 入参: numGlyphs 字形数量
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// 返回: []byte maxp表数据
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func buildTrueTypeMaxpTable(numGlyphs uint16) []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint32(0x00010000))
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binary.Write(buf, binary.BigEndian, uint16(numGlyphs))
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for i := 0; i < 13; i++ {
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binary.Write(buf, binary.BigEndian, uint16(0))
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}
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return buf.Bytes()
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}
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// buildOS2Table 构建OS/2表 (使用默认Metrics)
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// 返回: []byte OS/2表数据
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func buildOS2Table() []byte {
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return BuildOS2TableWithMetrics(800, -200)
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}
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// BuildOS2TableWithMetrics 构建OS/2表
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// 入参: ascender 上升部, descender 下降部
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// 返回: []byte OS/2表数据
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func BuildOS2TableWithMetrics(ascender, descender int16) []byte {
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os2 := new(bytes.Buffer)
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binary.Write(os2, binary.BigEndian, uint16(3))
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binary.Write(os2, binary.BigEndian, int16(500))
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binary.Write(os2, binary.BigEndian, uint16(400))
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binary.Write(os2, binary.BigEndian, uint16(5))
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binary.Write(os2, binary.BigEndian, uint16(0))
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binary.Write(os2, binary.BigEndian, int16(250))
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binary.Write(os2, binary.BigEndian, int16(250))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, int16(250))
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binary.Write(os2, binary.BigEndian, int16(250))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, int16(50))
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binary.Write(os2, binary.BigEndian, int16(250))
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binary.Write(os2, binary.BigEndian, int16(0))
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os2.Write(make([]byte, 10))
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binary.Write(os2, binary.BigEndian, uint32(0))
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binary.Write(os2, binary.BigEndian, uint32(0))
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binary.Write(os2, binary.BigEndian, uint32(0))
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binary.Write(os2, binary.BigEndian, uint32(0))
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os2.WriteString("PfEd")
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binary.Write(os2, binary.BigEndian, uint16(0x0040))
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binary.Write(os2, binary.BigEndian, uint16(0))
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binary.Write(os2, binary.BigEndian, uint16(255))
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binary.Write(os2, binary.BigEndian, ascender)
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binary.Write(os2, binary.BigEndian, descender)
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, uint16(ascender))
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if descender < 0 {
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binary.Write(os2, binary.BigEndian, uint16(-descender))
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} else {
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binary.Write(os2, binary.BigEndian, uint16(descender))
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}
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binary.Write(os2, binary.BigEndian, uint32(0))
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binary.Write(os2, binary.BigEndian, uint32(0))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, int16(0))
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binary.Write(os2, binary.BigEndian, uint16(0))
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binary.Write(os2, binary.BigEndian, uint16(0))
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binary.Write(os2, binary.BigEndian, uint16(0))
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return os2.Bytes()
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}
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// buildNameTable 构建name表 (最小化)
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// 返回: []byte name表数据
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func buildNameTable() []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, uint16(0))
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binary.Write(buf, binary.BigEndian, uint16(6))
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return buf.Bytes()
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}
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// BuildPostTable 构建post表 (版本3.0, 无字形名称)
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// 返回: []byte post表数据
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func BuildPostTable() []byte {
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buf := new(bytes.Buffer)
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binary.Write(buf, binary.BigEndian, uint32(0x00030000))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, int16(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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binary.Write(buf, binary.BigEndian, uint32(0))
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return buf.Bytes()
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}
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// buildHmtxTable 构建hmtx表
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// 入参: widths 宽度列表
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// 返回: []byte hmtx表数据
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func buildHmtxTable(widths []uint16) []byte {
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buf := new(bytes.Buffer)
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for _, w := range widths {
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binary.Write(buf, binary.BigEndian, uint16(w))
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binary.Write(buf, binary.BigEndian, int16(0))
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}
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return buf.Bytes()
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}
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// SerializeOTF 序列化OpenType字体结构，一次分配输出，不修改输入表数据
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// 复用各表校验和计算整份字体的调整值，不重复扫描表数据
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// 入参: tables 表数据映射
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// 返回: []byte 完整字体数据, error 错误信息
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func SerializeOTF(tables map[string][]byte) ([]byte, error) {
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if len(tables) > math.MaxUint16/16 {
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return nil, fmt.Errorf("too many font tables")
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}
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headerSize := 12 + 16*len(tables)
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size := uint64(headerSize)
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tags := make([]string, 0, len(tables))
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for tag, data := range tables {
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if len(tag) != 4 {
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return nil, fmt.Errorf("invalid font table tag %q", tag)
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}
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if tag == "head" && len(data) < 12 {
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return nil, fmt.Errorf("invalid head font table")
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}
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size += (uint64(len(data)) + 3) &^ 3
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if size > math.MaxUint32 || size > uint64(math.MaxInt) {
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return nil, fmt.Errorf("font table data too large")
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}
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tags = append(tags, tag)
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}
|
|
sort.Strings(tags)
|
|
data := make([]byte, int(size))
|
|
numTables := len(tables)
|
|
entrySelector := 0
|
|
for 1<<(entrySelector+1) <= numTables {
|
|
entrySelector++
|
|
}
|
|
searchRange := 1 << (entrySelector + 4)
|
|
rangeShift := numTables*16 - searchRange
|
|
if tables["CFF "] != nil || tables["CFF2"] != nil {
|
|
copy(data, "OTTO")
|
|
} else {
|
|
binary.BigEndian.PutUint32(data, 0x00010000)
|
|
}
|
|
binary.BigEndian.PutUint16(data[4:], uint16(numTables))
|
|
binary.BigEndian.PutUint16(data[6:], uint16(searchRange))
|
|
binary.BigEndian.PutUint16(data[8:], uint16(entrySelector))
|
|
binary.BigEndian.PutUint16(data[10:], uint16(rangeShift))
|
|
offset, adjustment := headerSize, 0
|
|
var checksum uint32
|
|
for i, tag := range tags {
|
|
table := tables[tag]
|
|
length := (len(table) + 3) &^ 3
|
|
padded := data[offset : offset+length]
|
|
copy(padded, table)
|
|
if tag == "head" {
|
|
clear(padded[8:12])
|
|
adjustment = offset + 8
|
|
}
|
|
record := data[12+i*16 : 28+i*16]
|
|
copy(record, tag)
|
|
tableChecksum := calcTableChecksum(padded)
|
|
checksum += tableChecksum
|
|
binary.BigEndian.PutUint32(record[4:], tableChecksum)
|
|
binary.BigEndian.PutUint32(record[8:], uint32(offset))
|
|
binary.BigEndian.PutUint32(record[12:], uint32(len(table)))
|
|
offset += length
|
|
}
|
|
if adjustment != 0 {
|
|
binary.BigEndian.PutUint32(data[adjustment:], 0xB1B0AFBA-checksum-calcTableChecksum(data[:headerSize]))
|
|
}
|
|
return data, nil
|
|
}
|