feat(强化兼容): 改进字体渲染

2026-08-30 12:12:40 +08:00 · 2026-01-07 15:29:08 +08:00
parent 191ff30b97
commit 308076a9f6
11 changed files with 2065 additions and 344 deletions
@@ -0,0 +1,140 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"encoding/binary"
+)
+
+// fixTrueType 尝试修复 TrueType/OpenType 字体数据
+// 入参: data 原始字体数据, fixCmap 是否修复cmap, fixName 是否修复name
+// 返回: bool 是否修复, []byte 修复后数据, map[rune]uint16 字符映射, bool 是否缺失cmap, error 错误信息
+func fixTrueType(data []byte, fixCmap, fixName bool) (bool, []byte, map[rune]uint16, bool, error) {
+	if len(data) < 12 {
+		return false, data, nil, false, nil
+	}
+	numTables := binary.BigEndian.Uint16(data[4:6])
+	existingTables := make(map[string][]byte)
+	pos := 12
+	for i := 0; i < int(numTables); i++ {
+		if len(data) < pos+16 {
+			break
+		}
+		tag := string(data[pos : pos+4])
+		offset := binary.BigEndian.Uint32(data[pos+8 : pos+12])
+		length := binary.BigEndian.Uint32(data[pos+12 : pos+16])
+		if uint32(len(data)) >= offset+length {
+			existingTables[tag] = data[offset : offset+length]
+		}
+		pos += 16
+	}
+	missingHead := existingTables["head"] == nil
+	missingMaxp := existingTables["maxp"] == nil
+	missingHhea := existingTables["hhea"] == nil
+	missingHmtx := existingTables["hmtx"] == nil
+	missingOS2 := existingTables["OS/2"] == nil
+	missingCmap := existingTables["cmap"] == nil
+	if !missingCmap {
+		if !hasUsableCmap(existingTables["cmap"]) {
+			missingCmap = true
+		}
+	}
+	missingName := existingTables["name"] == nil
+	missingPost := existingTables["post"] == nil
+	if !missingHead && !missingMaxp && !missingHhea && !missingHmtx &&
+		!missingOS2 && !missingCmap && !missingName && !missingPost {
+		return false, data, nil, false, nil
+	}
+	newTables := make(map[string][]byte)
+	for k, v := range existingTables {
+		newTables[k] = v
+	}
+	var numGlyphs uint16 = 0
+	if !missingMaxp {
+		maxp := existingTables["maxp"]
+		if len(maxp) >= 6 {
+			numGlyphs = binary.BigEndian.Uint16(maxp[4:6])
+		}
+	}
+	if numGlyphs == 0 {
+		numGlyphs = 255
+	}
+	if missingHead {
+		newTables["head"] = buildHeadTable(1000)
+	}
+	if missingMaxp {
+		newTables["maxp"] = buildMaxpTable(numGlyphs)
+	}
+	if missingHhea {
+		newTables["hhea"] = buildHheaTable(numGlyphs)
+	}
+	if missingHmtx {
+		defWidths := make([]uint16, numGlyphs)
+		for i := range defWidths {
+			defWidths[i] = 500
+		}
+		newTables["hmtx"] = buildHmtxTable(defWidths)
+	}
+	ascender := int16(800)
+	descender := int16(-200)
+	if hhea, ok := newTables["hhea"]; ok && len(hhea) >= 10 {
+		ascender = int16(binary.BigEndian.Uint16(hhea[4:6]))
+		descender = int16(binary.BigEndian.Uint16(hhea[6:8]))
+	}
+	if missingOS2 {
+		newTables["OS/2"] = buildOS2TableWithMetrics(ascender, descender)
+	}
+	var mapping map[rune]uint16
+	if missingCmap && fixCmap {
+		mapping = make(map[rune]uint16)
+		for i := uint16(0); i < numGlyphs; i++ {
+			mapping[rune(i)] = i
+		}
+		newTables["cmap"] = buildCmapTable(numGlyphs, mapping)
+	}
+	if missingName && fixName {
+		newTables["name"] = buildNameTable()
+	}
+	if missingPost {
+		newTables["post"] = buildPostTable()
+	}
+	finalData, err := serializeOTF(newTables)
+	if err != nil {
+		return false, data, nil, missingCmap, err
+	}
+	return true, finalData, mapping, missingCmap, nil
+}
+
+// hasUsableCmap 检查是否存在可用的 cmap 子表
+// 入参: data cmap表数据
+// 返回: bool 是否可用
+func hasUsableCmap(data []byte) bool {
+	if len(data) < 4 {
+		return false
+	}
+	numTables := binary.BigEndian.Uint16(data[2:4])
+	pos := 4
+	for i := 0; i < int(numTables); i++ {
+		if len(data) < pos+8 {
+			break
+		}
+		platformID := binary.BigEndian.Uint16(data[pos : pos+2])
+		if platformID == 0 || platformID == 3 {
+			return true
+		}
+		pos += 8
+	}
+	return false
+}