feat(归并文件): 归并文件下沉通用能力

internal/base/font/match.go

@@ -15,13 +15,147 @@
 package font
 
 import (
+	"bytes"
 	"path"
+	"slices"
+	"sort"
 	"strings"
 )
 
+// 字体匹配按精确、部分和模糊匹配排列，零值表示未匹配
+const (
+	MatchNone = iota
+	MatchExact
+	MatchPartial
+	MatchFuzzy
+)
+
+// matchRules 保存常用字体的名称、文件名及系统字体匹配规则
+var matchRules = normalizeMatchRules([]matchRule{
+	{
+		Keys:            []string{"小标宋", "方正小标宋", "xiaobiaosong", "fzxiaobiaosong", "fzxbs"},
+		Names:           []string{"小标宋体", "方正小标宋简体", "FZXiaoBiaoSong-B05", "FZXiaoBiaoSong-B05S"},
+		Files:           []string{"FZXBSJW.TTF", "fzxbs*.ttf", "fzxiaobiaosong*.ttf", "xiaobiaosong*.ttf"},
+		System:          "FZXiaoBiaoSong-B05S",
+		NoSyntheticBold: true,
+	},
+	{
+		Keys:   []string{"宋体", "新宋体", "simsun", "nsimsun", "simsunextb", "song", "songti", "stsong", "书宋", "方正书宋"},
+		Names:  []string{"宋体", "新宋体", "SimSun", "NSimSun", "SongTi", "STSong"},
+		Files:  []string{"simsun.ttc", "simsun.ttf", "nsimsun.ttf", "STSONG.TTF"},
+		System: "SimSun",
+	},
+	{
+		Keys:   []string{"黑体", "hei", "simhei", "heiti", "sthei", "方正黑体"},
+		Names:  []string{"黑体", "SimHei", "HeiTi", "STHeiti", "方正黑体简体"},
+		Files:  []string{"simhei.ttf", "STXIHEI.TTF", "FZHT_GB18030.TTF", "fzht*.ttf"},
+		System: "SimHei",
+	},
+	{
+		Keys:   []string{"楷体", "kai", "kaiti", "simkai", "stkaiti", "方正楷体"},
+		Names:  []string{"楷体", "KaiTi", "SimKai", "STKaiti", "方正楷体简体"},
+		Files:  []string{"simkai.ttf", "kaiti.ttf", "STKAITI.TTF", "FZKTJ.TTF", "fzkai*.ttf", "fzkt*.ttf"},
+		System: "KaiTi",
+	},
+	{
+		Keys:   []string{"仿宋", "fang", "fangsong", "simfang", "stfangsong", "方正仿宋"},
+		Names:  []string{"仿宋", "FangSong", "SimFang", "STFangsong", "方正仿宋简体"},
+		Files:  []string{"simfang.ttf", "fangsong.ttf", "STFANGSO.TTF", "FZFSJ.TTF", "fzfs*.ttf"},
+		System: "FangSong",
+	},
+	{
+		Keys:   []string{"微软雅黑", "microsoftyahei", "yahei", "msyh"},
+		Names:  []string{"微软雅黑", "Microsoft YaHei", "YaHei", "MSYH"},
+		Files:  []string{"msyh.ttc", "msyh.ttf"},
+		System: "Microsoft YaHei",
+	},
+	{
+		Keys:   []string{"arialblack"},
+		Names:  []string{"Arial Black", "ArialBlack"},
+		Files:  []string{"ariblk.ttf", "arial black*.ttf", "arialblack*.ttf"},
+		System: "Arial Black",
+	},
+	{
+		Keys:   []string{"arial"},
+		Names:  []string{"Arial"},
+		Files:  []string{"arial.ttf", "arial*.ttf"},
+		System: "Arial",
+	},
+	{
+		Keys:   []string{"helvetica"},
+		Names:  []string{"Helvetica", "Arial"},
+		Files:  []string{"arial.ttf", "arial*.ttf"},
+		System: "Arial",
+	},
+	{
+		Keys:   []string{"couriernew", "courier"},
+		Names:  []string{"Courier New", "CourierNew", "Courier"},
+		Files:  []string{"cour.ttf", "courier new*.ttf", "courier*.ttf"},
+		System: "Courier New",
+	},
+	{
+		Keys:   []string{"segoeui"},
+		Names:  []string{"Segoe UI", "SegoeUI"},
+		Files:  []string{"segoeui.ttf", "segoe*.ttf"},
+		System: "Segoe UI",
+	},
+	{
+		Keys:   []string{"timesnewroman", "times"},
+		Names:  []string{"Times New Roman", "TimesNewRoman"},
+		Files:  []string{"times.ttf", "times new roman*.ttf", "times*.ttf"},
+		System: "Times New Roman",
+	},
+})
+
 // fontNameReplacer 移除字体名称匹配时忽略的分隔符
 var fontNameReplacer = strings.NewReplacer(" ", "", "-", "", "_", "", "(", "", ")", "", "（", "", "）", "")
 
+// matchRule 字体匹配规则
+type matchRule struct {
+	Keys            []string
+	Names           []string
+	Files           []string
+	System          string
+	NoSyntheticBold bool
+}
+
+// FileCandidate 字体文件候选
+type FileCandidate struct {
+	Name       string
+	Face       int
+	base       string
+	lowerBase  string
+	filename   string
+	normalized string
+	names      []string
+	fold       string
+}
+
+// patternMatcher 字体文件匹配器
+type patternMatcher struct {
+	pattern      string
+	lowerPattern string
+	stem         string
+	aliases      []string
+	priority     int
+}
+
+// FileMatch 字体文件匹配结果
+type FileMatch struct {
+	Name      string
+	Face      int
+	Priority  int
+	Rank      int
+	styleRank int
+	sortName  string
+}
+
+// fileKey 字体文件与集合索引的去重键
+type fileKey struct {
+	Name string
+	Face int
+}
+
 // NormalizeName 规范化字体名称
 // 入参: name 字体名称
 // 返回: string 规范化后的字体名称
@@ -62,3 +196,611 @@ func AppendFontName(names []string, seen map[string]bool, name string) []string
 	seen[key] = true
 	return append(names, name)
 }
+
+// normalizeMatchRules 预处理固定字体规则的匹配名称，保留候选名称及顺序
+// 入参: rules 字体匹配规则
+// 返回: []matchRule 预处理后的规则
+func normalizeMatchRules(rules []matchRule) []matchRule {
+	for i := range rules {
+		rule := &rules[i]
+		keys := append(append(rule.Keys, rule.Names...), rule.System)
+		rule.Keys = nil
+		for _, key := range keys {
+			key = NormalizeName(key)
+			if key != "" && !slices.Contains(rule.Keys, key) {
+				rule.Keys = append(rule.Keys, key)
+			}
+		}
+	}
+	return rules
+}
+
+// CandidateNames 获取字体候选名称
+// 入参: names 字体名称列表
+// 返回: []string 字体候选名称
+func CandidateNames(names ...string) []string {
+	return candidateNamesByLevel(MatchFuzzy, names...)
+}
+
+// ExactCandidateNames 获取精确字体候选名称
+// 入参: names 字体名称列表
+// 返回: []string 精确字体候选名称
+func ExactCandidateNames(names ...string) []string {
+	return candidateNamesByLevel(MatchExact, names...)
+}
+
+// qualifiedNames 获取保留名称后缀的字体候选
+// 入参: name 字体名称
+// 返回: []string 保留后缀的候选名称
+func qualifiedNames(name string) []string {
+	name = NormalizeName(name)
+	key := NormalizeName(name)
+	var names []string
+	seen := make(map[string]bool)
+	for _, rule := range matchRules {
+		if ruleMatchLevel(rule, key) != MatchPartial {
+			continue
+		}
+		prefix := ""
+		for _, alias := range rule.Keys {
+			if len(alias) > len(prefix) && strings.HasPrefix(name, alias) {
+				prefix = alias
+			}
+		}
+		suffix := strings.TrimPrefix(name, prefix)
+		for _, alias := range append([]string{rule.System}, rule.Names...) {
+			names = AppendFontName(names, seen, NormalizeName(alias)+suffix)
+		}
+	}
+	return names
+}
+
+// candidateNamesByLevel 获取指定等级内的字体候选名称
+// 入参: maxLevel 最大匹配等级, names 字体名称列表
+// 返回: []string 字体候选名称
+func candidateNamesByLevel(maxLevel int, names ...string) []string {
+	var result []string
+	seen := make(map[string]bool)
+	var bases []string
+	for _, name := range names {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			continue
+		}
+		result = AppendFontName(result, seen, name)
+		bases = append(bases, name)
+	}
+	levels := matchLevels(bases)
+	for level := MatchExact; level <= maxLevel; level++ {
+		for i := range bases {
+			for j, rule := range matchRules {
+				if levels[i*len(matchRules)+j] == level {
+					result = AppendFontName(result, seen, rule.System)
+					for _, item := range rule.Names {
+						result = AppendFontName(result, seen, item)
+					}
+				}
+			}
+		}
+	}
+	return result
+}
+
+// patternStem 获取字体匹配模式主干
+// 入参: pattern 字体文件匹配模式
+// 返回: string 字体匹配模式主干
+func patternStem(pattern string) string {
+	stem := strings.TrimSuffix(pattern, "*")
+	if IsFontFileName(stem) {
+		stem = strings.TrimSuffix(stem, path.Ext(stem))
+	}
+	if index := strings.IndexAny(stem, "*?["); index >= 0 {
+		stem = stem[:index]
+	}
+	return NormalizeName(stem)
+}
+
+// FilePatterns 获取字体文件匹配模式
+// 入参: names 字体名称列表
+// 返回: []string 字体文件匹配模式
+func FilePatterns(names ...string) []string {
+	var result []string
+	seen := make(map[string]bool)
+	levels := matchLevels(names)
+	for level := MatchExact; level <= MatchFuzzy; level++ {
+		for _, name := range candidateNamesAtLevel(level, names, levels) {
+			result = appendPattern(result, seen, name+"*")
+		}
+		for i := range names {
+			for j, rule := range matchRules {
+				if levels[i*len(matchRules)+j] == level {
+					for _, item := range rule.Files {
+						result = appendPattern(result, seen, item)
+					}
+				}
+			}
+		}
+	}
+	return result
+}
+
+// SystemNames 获取系统字体名称
+// 入参: names 字体名称列表
+// 返回: []string 系统字体名称
+func SystemNames(names ...string) []string {
+	var result []string
+	seen := make(map[string]bool)
+	for _, name := range names {
+		for _, item := range candidateNamesByLevel(MatchPartial, name) {
+			result = AppendFontName(result, seen, item)
+		}
+	}
+	return result
+}
+
+// candidateNamesAtLevel 获取指定等级的字体候选名称
+// 入参: level 匹配等级, names 字体名称列表, levels 名称与规则的匹配等级
+// 返回: []string 字体候选名称
+func candidateNamesAtLevel(level int, names []string, levels []int) []string {
+	var result []string
+	seen := make(map[string]bool)
+	for i, name := range names {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			continue
+		}
+		if level == MatchExact {
+			result = AppendFontName(result, seen, name)
+		}
+		for j, rule := range matchRules {
+			if levels[i*len(matchRules)+j] == level {
+				result = AppendFontName(result, seen, rule.System)
+				for _, item := range rule.Names {
+					result = AppendFontName(result, seen, item)
+				}
+			}
+		}
+	}
+	return result
+}
+
+// DefaultSystemNames 获取默认系统字体名称
+// 返回: []string 默认系统字体名称
+func DefaultSystemNames() []string {
+	return []string{
+		"SimSun", "Microsoft YaHei", "SimHei", "KaiTi", "FangSong",
+		"Noto Sans CJK SC", "Source Han Sans SC", "Arial", "Segoe UI", "Times New Roman",
+	}
+}
+
+// NoSyntheticBold 判断字体是否禁用合成粗体
+// 入参: names 字体名称列表
+// 返回: bool 是否禁用合成粗体
+func NoSyntheticBold(names ...string) bool {
+	for _, name := range names {
+		name = NormalizeName(name)
+		for _, rule := range matchRules {
+			if !rule.NoSyntheticBold {
+				continue
+			}
+			level := ruleMatchLevel(rule, name)
+			if level >= MatchExact && level <= MatchPartial {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// matchLevels 按名称和规则顺序计算匹配等级
+// 入参: names 字体名称列表
+// 返回: []int 名称与规则的匹配等级
+func matchLevels(names []string) []int {
+	levels := make([]int, len(names)*len(matchRules))
+	for i, name := range names {
+		name = NormalizeName(name)
+		for j, rule := range matchRules {
+			levels[i*len(matchRules)+j] = ruleMatchLevel(rule, name)
+		}
+	}
+	return levels
+}
+
+// ruleMatchLevel 获取字体规则匹配等级
+// 入参: rule 字体匹配规则, name 规范化后的字体名称
+// 返回: int 匹配等级
+func ruleMatchLevel(rule matchRule, name string) int {
+	if name == "" {
+		return MatchNone
+	}
+	level := MatchNone
+	for _, item := range rule.Keys {
+		if name == item {
+			return MatchExact
+		}
+		if strings.HasPrefix(name, item) {
+			level = MatchPartial
+		} else if level == MatchNone && strings.Contains(name, item) {
+			level = MatchFuzzy
+		}
+	}
+	return level
+}
+
+// appendPattern 追加字体文件匹配模式
+// 入参: patterns 匹配模式列表, seen 去重映射, pattern 匹配模式
+// 返回: []string 匹配模式列表
+func appendPattern(patterns []string, seen map[string]bool, pattern string) []string {
+	pattern = strings.TrimSpace(pattern)
+	if pattern == "" {
+		return patterns
+	}
+	key := strings.ToLower(pattern)
+	if seen[key] {
+		return patterns
+	}
+	seen[key] = true
+	return append(patterns, pattern)
+}
+
+// AppendFileNames 建立各字体的内部名称与文件别名匹配候选
+// 入参: candidates 字体候选, index 文件候选索引, faces 各字体内部名称
+// 返回: []FileCandidate 字体候选列表
+func AppendFileNames(candidates []FileCandidate, index int, faces [][]string) []FileCandidate {
+	file := candidates[index]
+	replaced := false
+	for face, names := range faces {
+		file.Face = face
+		file.names = make([]string, len(names))
+		for i, name := range names {
+			file.names[i] = NormalizeName(name)
+		}
+		for _, name := range file.names {
+			file.normalized = name
+			if !replaced {
+				candidates[index] = file
+				replaced = true
+			} else {
+				candidates = append(candidates, file)
+			}
+		}
+	}
+	return candidates
+}
+
+// CollectionIndex 按内部名称与样式选择集合项，未匹配时保留首项
+// 入参: data 集合数据, names 字体名称, bold 是否粗体, italic 是否斜体
+// 返回: int 零起始字体索引
+func CollectionIndex(data []byte, names []string, bold, italic bool) int {
+	return NameIndex(FileNames(bytes.NewReader(data)), names, bold, italic)
+}
+
+// NameIndex 按名称与样式选择字体索引，未匹配时保留首项
+// 入参: faces 各字体名称, names 目标名称, bold 是否粗体, italic 是否斜体
+// 返回: int 零起始字体索引
+func NameIndex(faces [][]string, names []string, bold, italic bool) int {
+	candidates := AppendFileNames([]FileCandidate{{}}, 0, faces)
+	if matches := FileMatches(candidates, names, bold, italic); len(matches) > 0 {
+		return matches[0].Face
+	}
+	return 0
+}
+
+// FileMatches 匹配字体文件候选
+// 入参: candidates 字体候选, names 字体名称, bold 是否粗体, italic 是否斜体
+// 返回: []FileMatch 按优先级排列的字体匹配
+func FileMatches(candidates []FileCandidate, names []string, bold, italic bool) []FileMatch {
+	matches := make([]FileMatch, 0, len(candidates))
+	seen := make(map[fileKey]int, len(candidates))
+	if len(names) == 0 {
+		for _, name := range DefaultSystemNames() {
+			matches = append(matches, FileMatches(candidates, []string{name}, bold, italic)...)
+		}
+		sort.SliceStable(matches, func(i, j int) bool {
+			return matches[i].Rank < matches[j].Rank
+		})
+		unique := matches[:0]
+		for _, match := range matches {
+			key := fileKey{strings.ToLower(match.Name), match.Face}
+			if _, ok := seen[key]; !ok {
+				seen[key] = len(unique)
+				unique = append(unique, match)
+			}
+		}
+		return unique
+	}
+	for i, name := range names {
+		if name == "" {
+			continue
+		}
+		for j, alias := range append([]string{name}, qualifiedNames(name)...) {
+			matcher := patternMatcher{stem: NormalizeName(alias), priority: (i-len(names))*2 + min(j, 1)}
+			if matcher.stem == "" {
+				continue
+			}
+			for _, file := range candidates {
+				if rank := matcher.rankCandidate(file); rank == MatchExact {
+					appendFileMatch(&matches, seen, matcher, file, rank, bold, italic)
+				}
+			}
+		}
+	}
+	for _, matcher := range newPatternMatchers(FilePatterns(names...)) {
+		for _, file := range candidates {
+			rank := matcher.rankCandidate(file)
+			appendFileMatch(&matches, seen, matcher, file, rank, bold, italic)
+		}
+	}
+	sortFileMatches(matches)
+	return matches
+}
+
+// FileCandidates 筛选字体文件候选
+// 入参: names 文件名列表, base 文件名提取函数
+// 返回: []FileCandidate 字体文件候选列表
+func FileCandidates(names []string, base func(string) string) []FileCandidate {
+	files := make([]FileCandidate, 0, len(names))
+	for _, name := range names {
+		if IsFontFileName(name) {
+			baseName := base(name)
+			normalized := NormalizeName(strings.TrimSuffix(baseName, path.Ext(baseName)))
+			files = append(files, FileCandidate{
+				Name:       name,
+				base:       baseName,
+				lowerBase:  strings.ToLower(baseName),
+				filename:   normalized,
+				normalized: normalized,
+				fold:       strings.ToLower(name),
+			})
+		}
+	}
+	return files
+}
+
+// newPatternMatcher 创建字体文件匹配器
+// 入参: pattern 匹配模式
+// 返回: patternMatcher 字体文件匹配器
+func newPatternMatcher(pattern string) patternMatcher {
+	matcher := patternMatcher{
+		pattern:      pattern,
+		lowerPattern: strings.ToLower(pattern),
+		stem:         patternStem(pattern),
+	}
+	if matcher.stem != "" {
+		for _, alias := range ExactCandidateNames(matcher.stem) {
+			alias = NormalizeName(alias)
+			if alias != "" {
+				matcher.aliases = append(matcher.aliases, alias)
+			}
+		}
+	}
+	return matcher
+}
+
+// newPatternMatchers 创建字体文件匹配器列表
+// 入参: patterns 匹配模式列表
+// 返回: []patternMatcher 字体文件匹配器列表
+func newPatternMatchers(patterns []string) []patternMatcher {
+	matchers := make([]patternMatcher, 0, len(patterns))
+	for priority, pattern := range patterns {
+		matcher := newPatternMatcher(pattern)
+		matcher.priority = priority
+		matchers = append(matchers, matcher)
+	}
+	return matchers
+}
+
+// rankCandidate 获取字体文件候选匹配等级
+// 入参: file 字体文件候选
+// 返回: int 匹配等级
+func (m patternMatcher) rankCandidate(file FileCandidate) int {
+	exactPath, _ := path.Match(m.pattern, file.base)
+	lowerPath, _ := path.Match(m.lowerPattern, file.lowerBase)
+	if m.stem == "" {
+		if exactPath || lowerPath {
+			return MatchFuzzy
+		}
+		return MatchNone
+	}
+	name := m.candidateName(file)
+	if name == m.stem {
+		return MatchExact
+	}
+	for _, alias := range m.aliases {
+		if name == alias {
+			return MatchExact
+		}
+	}
+	if fileKnownStyleSuffix(m.styleSuffixNormalized(name)) {
+		return MatchExact
+	}
+	if strings.HasPrefix(name, m.stem) {
+		return MatchPartial
+	}
+	for _, alias := range m.aliases {
+		if strings.HasPrefix(name, alias) {
+			return MatchPartial
+		}
+	}
+	if exactPath || lowerPath || strings.Contains(name, m.stem) {
+		return MatchFuzzy
+	}
+	for _, alias := range m.aliases {
+		if strings.Contains(name, alias) {
+			return MatchFuzzy
+		}
+	}
+	return MatchNone
+}
+
+// candidateName 保留同族内部名称的区分，只有无关联时使用调用方文件别名
+// 入参: file 字体文件候选
+// 返回: string 用于统一匹配名称与样式的规范名称
+func (m patternMatcher) candidateName(file FileCandidate) string {
+	if len(file.names) == 0 || file.base == "" || m.stem == "" {
+		return file.normalized
+	}
+	for _, name := range file.names {
+		if strings.HasPrefix(name, m.stem) {
+			return file.normalized
+		}
+		for _, alias := range m.aliases {
+			if strings.HasPrefix(name, alias) {
+				return file.normalized
+			}
+		}
+	}
+	return file.filename
+}
+
+// styleSuffixNormalized 获取规范字体名称的样式后缀
+// 入参: name 规范字体名称
+// 返回: string 样式后缀
+func (m patternMatcher) styleSuffixNormalized(name string) string {
+	if m.stem == "" || name == "" {
+		return ""
+	}
+	if strings.HasPrefix(name, m.stem) {
+		return strings.TrimPrefix(name, m.stem)
+	}
+	for _, alias := range m.aliases {
+		if strings.HasPrefix(name, alias) {
+			return strings.TrimPrefix(name, alias)
+		}
+	}
+	return ""
+}
+
+// appendFileMatch 追加字体文件匹配结果
+// 入参: matches 匹配结果, seen 已匹配文件, matcher 匹配器, file 字体文件候选, rank 匹配等级, bold 是否粗体, italic 是否斜体
+func appendFileMatch(matches *[]FileMatch, seen map[fileKey]int, matcher patternMatcher, file FileCandidate, rank int, bold, italic bool) {
+	if rank == MatchNone {
+		return
+	}
+	suffix := matcher.styleSuffixNormalized(matcher.candidateName(file))
+	if rank == MatchFuzzy {
+		suffix = matcher.styleSuffixNormalized(NormalizeName(file.base))
+	}
+	next := FileMatch{
+		Name:      file.Name,
+		Face:      file.Face,
+		Priority:  matcher.priority,
+		Rank:      rank,
+		styleRank: fileStyleRank(suffix, bold, italic),
+		sortName:  file.lowerBase,
+	}
+	key := fileKey{file.fold, file.Face}
+	if index, ok := seen[key]; ok {
+		if fileMatchLess(next, (*matches)[index]) {
+			(*matches)[index] = next
+		}
+		return
+	}
+	seen[key] = len(*matches)
+	*matches = append(*matches, next)
+}
+
+// sortFileMatches 排序字体文件匹配结果
+// 入参: matches 匹配结果
+func sortFileMatches(matches []FileMatch) {
+	sort.SliceStable(matches, func(i, j int) bool {
+		return fileMatchLess(matches[i], matches[j])
+	})
+}
+
+// fileMatchLess 判断字体文件匹配结果优先级
+// 入参: left 左侧匹配结果, right 右侧匹配结果
+// 返回: bool 左侧是否优先
+func fileMatchLess(left, right FileMatch) bool {
+	if left.Priority != right.Priority {
+		return left.Priority < right.Priority
+	}
+	if left.Rank != right.Rank {
+		return left.Rank < right.Rank
+	}
+	if left.styleRank != right.styleRank {
+		return left.styleRank < right.styleRank
+	}
+	return left.sortName < right.sortName
+}
+
+// FileMatchNames 获取字体文件匹配名称
+// 入参: matches 匹配结果
+// 返回: []string 字体文件列表
+func FileMatchNames(matches []FileMatch) []string {
+	names := make([]string, 0, len(matches))
+	seen := make(map[string]bool, len(matches))
+	for _, match := range matches {
+		key := strings.ToLower(match.Name)
+		if !seen[key] {
+			seen[key] = true
+			names = append(names, match.Name)
+		}
+	}
+	return names
+}
+
+// fileStyleRank 获取字体文件样式匹配等级
+// 入参: suffix 样式后缀, bold 是否粗体, italic 是否斜体
+// 返回: int 样式匹配等级
+func fileStyleRank(suffix string, bold, italic bool) int {
+	fileBold, fileItalic := fileStyleFromSuffix(suffix)
+	rank := 0
+	if fileBold != bold {
+		rank += 2
+	}
+	if fileItalic != italic {
+		rank += 2
+	}
+	if !bold && !italic && !fileBold && !fileItalic && suffix != "" && !fileRegularSuffix(suffix) {
+		rank++
+	}
+	return rank
+}
+
+// fileStyleFromSuffix 获取样式后缀对应的字体样式
+// 入参: suffix 样式后缀
+// 返回: bool 是否粗体, bool 是否斜体
+func fileStyleFromSuffix(suffix string) (bool, bool) {
+	bold := suffix == "b" ||
+		suffix == "bd" ||
+		suffix == "bold" ||
+		suffix == "bi" ||
+		suffix == "bolditalic" ||
+		suffix == "boldoblique"
+	italic := suffix == "i" ||
+		suffix == "it" ||
+		suffix == "italic" ||
+		suffix == "oblique" ||
+		suffix == "bi" ||
+		suffix == "bolditalic" ||
+		suffix == "boldoblique"
+	return bold, italic
+}
+
+// fileRegularSuffix 判断是否为常规样式后缀
+// 入参: suffix 样式后缀
+// 返回: bool 是否为常规样式后缀
+func fileRegularSuffix(suffix string) bool {
+	switch suffix {
+	case "r", "regular", "normal", "常规":
+		return true
+	default:
+		return false
+	}
+}
+
+// fileKnownStyleSuffix 判断是否为已知样式后缀
+// 入参: suffix 样式后缀
+// 返回: bool 是否为已知样式后缀
+func fileKnownStyleSuffix(suffix string) bool {
+	switch suffix {
+	case "r", "regular", "normal", "常规",
+		"b", "bd", "bold",
+		"i", "it", "italic", "oblique",
+		"bi", "bolditalic", "boldoblique":
+		return true
+	default:
+		return false
+	}
+}

internal/base/geom/clip.go

@@ -0,0 +1,129 @@
+// 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 geom
+
+import "math"
+
+// polygonPoint 允许同结构的后端顶点直接参与裁剪，避免整片坐标转换
+type polygonPoint interface {
+	~struct{ X, Y float64 }
+}
+
+// ClipPolygon 按非退化凸窗口逐边裁剪多边形，保留原顶点绕向，不修改输入
+// 入参: a 绘制顶点, b 已通过ConvexPolygon检查的裁剪顶点，均不含重复闭合点
+// 返回: []P 交集顶点，少于三个顶点时不构成区域, bool 是否满足数值精度
+func ClipPolygon[P polygonPoint](a, b []P) ([]P, bool) {
+	for i, start := range b {
+		origin, end := Point(start), Point(b[(i+1)%len(b)])
+		dx, dy := end.X-origin.X, end.Y-origin.Y
+		length := math.Hypot(dx, dy)
+		if length == 0 {
+			continue
+		}
+		dx, dy = dx/length, dy/length
+		distance := func(p P) float64 { return convexDistance(origin, Point(p), dx, dy) }
+		sign := 1.0
+		for _, p := range b {
+			if d := distance(p); d != 0 {
+				sign = math.Copysign(1, d)
+				break
+			}
+		}
+		if len(a) == 0 {
+			break
+		}
+		var clipped []P
+		appendPoint := func(p P) {
+			if len(clipped) == 0 || p != clipped[len(clipped)-1] {
+				clipped = append(clipped, p)
+			}
+		}
+		previous := a[len(a)-1]
+		previousDistance := sign * distance(previous)
+		if !finite(previousDistance) {
+			return nil, false
+		}
+		for _, p := range a {
+			d := sign * distance(p)
+			if !finite(d) {
+				return nil, false
+			}
+			if (d >= 0) != (previousDistance >= 0) {
+				scale := math.Max(math.Abs(d), math.Abs(previousDistance))
+				fraction := (previousDistance / scale) / (previousDistance/scale - d/scale)
+				intersection := Lerp(Point(previous), Point(p), fraction)
+				if dx == 0 {
+					intersection.X = origin.X
+				}
+				if dy == 0 {
+					intersection.Y = origin.Y
+				}
+				appendPoint(P(intersection))
+			}
+			if d >= 0 {
+				appendPoint(p)
+			}
+			previous, previousDistance = p, d
+		}
+		if len(clipped) > 1 && clipped[0] == clipped[len(clipped)-1] {
+			clipped = clipped[:len(clipped)-1]
+		}
+		a = clipped
+	}
+	return a, true
+}
+
+// ConvexPolygon 检查所有顶点位于各边的同一侧，不修改输入
+// 入参: points 不含重复闭合点的独立顶点
+// 返回: []P 原顶点，非有限距离或异侧顶点返回nil, bool 是否为非退化凸多边形
+func ConvexPolygon[P polygonPoint](points []P) ([]P, bool) {
+	positive := false
+	for i, start := range points {
+		origin, end := Point(start), Point(points[(i+1)%len(points)])
+		dx, dy := end.X-origin.X, end.Y-origin.Y
+		length := math.Hypot(dx, dy)
+		if !finite(length) {
+			return nil, false
+		}
+		if length == 0 {
+			continue
+		}
+		dx, dy = dx/length, dy/length
+		sign := 0.0
+		for _, p := range points {
+			d := convexDistance(origin, Point(p), dx, dy)
+			if !finite(d) || sign*d < 0 {
+				return nil, false
+			}
+			if d != 0 {
+				sign, positive = math.Copysign(1, d), true
+			}
+		}
+	}
+	return points, positive
+}
+
+// convexDistance 按浮点乘法误差界识别共线点，不使用固定坐标容差
+// 入参: start 边起点, point 待测顶点, dx 横向单位分量, dy 纵向单位分量
+// 返回: float64 顶点到边的有向距离
+func convexDistance(start, point Point, dx, dy float64) float64 {
+	x, y := point.X-start.X, point.Y-start.Y
+	distance := math.FMA(dx, y, -dy*x)
+	errorBound := (math.Abs(dx*y) + math.Abs(dy*x)) * 0x1p-49
+	if finite(errorBound) && math.Abs(distance) <= errorBound {
+		return 0
+	}
+	return distance
+}

internal/base/image/metadata.go

@@ -20,8 +20,20 @@ import (
 	"encoding/binary"
 	"fmt"
 	"hash/crc32"
+	"image"
+	"math"
+	"math/big"
 )
 
+// PNGDensityChunkSize 为PNG像素密度块占用的字节数
+const PNGDensityChunkSize = 21
+
+// Density 保存横纵像素密度，Unit为0表示比例、1表示每米像素数
+type Density struct {
+	X, Y float64
+	Unit byte
+}
+
 // PageInfo 图片方向与像素密度，不改变原始编码
 type PageInfo struct {
 	Orientation int
@@ -232,3 +244,179 @@ func imageExifMetadata(data []byte, dpi float64, directory uint32) (int, float64
 	}
 	return orientation, x, y, nil
 }
+
+// BMPDensity 提取已校验BMP头中的每米像素数
+// 入参: data 含至少40字节信息头的BMP编码
+// 返回: Density 像素密度, bool 密度是否可保留
+func BMPDensity(data []byte) (Density, bool) {
+	xdpi, ydpi := int32(binary.LittleEndian.Uint32(data[38:42])), int32(binary.LittleEndian.Uint32(data[42:46]))
+	if xdpi < 0 || ydpi < 0 {
+		return Density{}, false
+	}
+	return Density{X: float64(xdpi), Y: float64(ydpi), Unit: 1}, true
+}
+
+// TIFFConversionDensity 校验可转换的TIFF字段并提取规范化后的像素密度
+// 色彩配置、预乘透明度、扩展字段及其他目录需保留原始编码
+// 入参: data TIFF编码, layout 已校验的主图布局
+// 返回: Density PNG像素密度, bool 是否可完整转换
+func TIFFConversionDensity(data []byte, layout TIFFLayout) (Density, bool) {
+	var density Density
+	var order binary.ByteOrder = binary.LittleEndian
+	if data[0] == 'M' {
+		order = binary.BigEndian
+	}
+	if layout.Next != 0 || layout.Offset != order.Uint32(data[4:]) || layout.Reduced {
+		return density, false
+	}
+	offset := int(layout.Offset)
+	count := int(order.Uint16(data[offset:]))
+	unit := uint32(2)
+	var resolutions [2][2]uint32
+	for i := range count {
+		entry := data[offset+2+i*12 : offset+14+i*12]
+		tag, kind, number := order.Uint16(entry), order.Uint16(entry[2:]), order.Uint32(entry[4:])
+		value := order.Uint32(entry[8:])
+		if kind == 3 && number == 1 {
+			value = uint32(order.Uint16(entry[8:]))
+		}
+		switch tag {
+		case 256, 257, 258, 259, 273, 274, 277, 278, 279, 320, 322, 323, 324, 325:
+		case 262:
+			if value == 5 {
+				return density, false
+			}
+		case 254:
+			if value != 0 {
+				return density, false
+			}
+		case 255:
+			if value != 1 {
+				return density, false
+			}
+		case 266:
+			if kind != 3 || number != 1 || value != 1 && value != 2 {
+				return density, false
+			}
+		case 284:
+			if kind != 3 || number != 1 || value != 1 && value != 2 {
+				return density, false
+			}
+		case 292, 293:
+			mask := uint32(7)
+			if tag == 293 {
+				mask = 2
+			}
+			if kind != 4 || number != 1 || value & ^mask != 0 {
+				return density, false
+			}
+		case 317:
+			if kind != 3 || number != 1 || value != 1 && value != 2 {
+				return density, false
+			}
+		case 338:
+			if kind != 3 || number != 1 || value != 2 {
+				return density, false
+			}
+		case 339:
+			if kind != 3 || number == 0 || number > 4 {
+				return density, false
+			}
+			values := entry[8:]
+			if number > 2 {
+				if uint64(value)+uint64(number)*2 > uint64(len(data)) {
+					return density, false
+				}
+				values = data[value:]
+			}
+			for j := uint32(0); j < number; j++ {
+				if order.Uint16(values[j*2:]) != 1 {
+					return density, false
+				}
+			}
+		case 282, 283:
+			if kind != 5 || number != 1 || uint64(value)+8 > uint64(len(data)) {
+				return density, false
+			}
+			resolutions[tag-282] = [2]uint32{order.Uint32(data[value:]), order.Uint32(data[value+4:])}
+		case 296:
+			if kind != 3 || number != 1 || value < 1 || value > 3 {
+				return density, false
+			}
+			unit = value
+		default:
+			return density, false
+		}
+	}
+	if resolutions == [2][2]uint32{} {
+		return density, true
+	}
+	x, y := resolutions[0], resolutions[1]
+	if x[0] == 0 || x[1] == 0 || y[0] == 0 || y[1] == 0 {
+		return density, false
+	}
+	if unit == 1 {
+		a, b := uint64(x[0])*uint64(y[1]), uint64(y[0])*uint64(x[1])
+		divisor, next := a, b
+		for next != 0 {
+			divisor, next = next, divisor%next
+		}
+		density.X, density.Y = float64(a/divisor), float64(b/divisor)
+	} else {
+		factor := 1 / 0.0254
+		if unit == 3 {
+			factor = 100
+		}
+		density = Density{X: float64(x[0]) / float64(x[1]) * factor, Y: float64(y[0]) / float64(y[1]) * factor, Unit: 1}
+	}
+	if math.Round(density.X) < 1 || math.Round(density.Y) < 1 || math.Round(density.X) > math.MaxInt32 || math.Round(density.Y) > math.MaxInt32 {
+		return density, false
+	}
+	if layout.Orientation >= 5 {
+		density.X, density.Y = density.Y, density.X
+	}
+	return density, true
+}
+
+// Scale 按最终像素尺寸保留绝对密度或精确相对比例
+// 入参: before 原始像素尺寸, after 最终像素尺寸
+// 返回: Density 缩放后密度, bool 相对比例是否可完整保留
+func (density Density) Scale(before, after image.Point) (Density, bool) {
+	hasDensity := density.X != 0 || density.Y != 0
+	if hasDensity && before != after {
+		if density.Unit == 0 {
+			ratio := new(big.Rat).SetFrac64(int64(density.X)*int64(after.X), int64(density.Y)*int64(after.Y))
+			ratio.Mul(ratio, new(big.Rat).SetFrac64(int64(before.Y), int64(before.X)))
+			if ratio.Num().BitLen() > 31 || ratio.Denom().BitLen() > 31 {
+				return density, false
+			}
+			density.X, density.Y = float64(ratio.Num().Int64()), float64(ratio.Denom().Int64())
+		} else {
+			density.X *= float64(after.X) / float64(before.X)
+			density.Y *= float64(after.Y) / float64(before.Y)
+		}
+	}
+	return density, true
+}
+
+// WithPNGDensity 在无密度块的PNG头后插入pHYs，保留源编码不变
+// 入参: data 完整PNG编码, density 像素密度
+// 返回: []byte 带密度的编码, bool 密度是否可完整保留
+func WithPNGDensity(data []byte, density Density) ([]byte, bool) {
+	x, y := math.Round(density.X), math.Round(density.Y)
+	if x > math.MaxInt32 || y > math.MaxInt32 || density.X > 0 && x < 1 || density.Y > 0 && y < 1 {
+		return nil, false
+	}
+	chunk := make([]byte, 21)
+	binary.BigEndian.PutUint32(chunk, 9)
+	copy(chunk[4:], "pHYs")
+	binary.BigEndian.PutUint32(chunk[8:], uint32(x))
+	binary.BigEndian.PutUint32(chunk[12:], uint32(y))
+	chunk[16] = density.Unit
+	binary.BigEndian.PutUint32(chunk[17:], crc32.ChecksumIEEE(chunk[4:17]))
+	output := make([]byte, 0, len(data)+PNGDensityChunkSize)
+	output = append(output, data[:33]...)
+	output = append(output, chunk...)
+	output = append(output, data[33:]...)
+	return output, true
+}

internal/base/image/scale.go

@@ -0,0 +1,285 @@
+// 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 image
+
+import (
+	"image"
+	"image/color"
+	"math"
+	"slices"
+
+	"golang.org/x/image/draw"
+	"golang.org/x/image/math/f64"
+)
+
+// rasterScaleBufferLimit 限制整像素缩放器的浮点中间缓冲，超出时使用逐行采样
+const rasterScaleBufferLimit = 8 << 20
+
+// rasterAxisSample 保存目标像素及其归一化源采样权重
+type rasterAxisSample struct {
+	pixel   int
+	first   int
+	weights []float64
+}
+
+// rasterImagePixel 保存未取整或裁切的预乘颜色累积值
+type rasterImagePixel struct {
+	r, g, b, a float64
+}
+
+// rasterImageRow 保存正在累积的目标行
+type rasterImageRow struct {
+	sample rasterAxisSample
+	values []rasterImagePixel
+}
+
+// rasterImageSource 为通用图片提供预乘十六位采样
+type rasterImageSource struct{ image.Image }
+
+// RGBA64At 读取通用颜色的原始预乘分量
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.RGBA64 预乘颜色
+func (s rasterImageSource) RGBA64At(x, y int) color.RGBA64 {
+	r, g, b, a := s.At(x, y).RGBA()
+	return color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)}
+}
+
+// drawRasterAxisImage 按像素中心进行轴向缩小，逐行复用横向采样并保留镜像与小数坐标
+// 入参: dst 目标图像, src 源图像, m 像素变换, op 合成操作
+// 返回: bool 是否使用轴向采样
+func drawRasterAxisImage(dst draw.Image, src image.Image, m [6]float64, op draw.Op) bool {
+	sx, sy := math.Abs(m[0]), math.Abs(m[3])
+	if m[1] != 0 || m[2] != 0 || sx == 0 || sy == 0 || sx > 1 || sy > 1 || sx == 1 && sy == 1 {
+		return false
+	}
+	for _, v := range m {
+		if math.IsNaN(v) || math.IsInf(v, 0) {
+			return false
+		}
+	}
+	b := src.Bounds()
+	if b.Empty() {
+		return true
+	}
+	r := TransformBounds(b, m, dst.Bounds())
+	if r.Empty() {
+		return true
+	}
+	xs := rasterImageAxis(r.Min.X, r.Max.X, b.Min.X, b.Max.X, m[0], m[4])
+	ys := rasterImageAxis(r.Min.Y, r.Max.Y, b.Min.Y, b.Max.Y, m[3], m[5])
+	if len(xs) == 0 || len(ys) == 0 {
+		return true
+	}
+	if m[3] < 0 {
+		slices.Reverse(ys)
+	}
+	pixels, ok := src.(image.RGBA64Image)
+	if !ok {
+		pixels = rasterImageSource{src}
+	}
+	width := len(xs)
+	horizontal := make([]rasterImagePixel, width)
+	columns := make([]int, width)
+	output := image.NewRGBA64(image.Rect(0, 0, width, 1))
+	var active []rasterImageRow
+	var free [][]rasterImagePixel
+	next := 0
+	for y := ys[0].first; next < len(ys) || len(active) != 0; y++ {
+		if len(active) == 0 && y < ys[next].first {
+			y = ys[next].first
+		}
+		for next < len(ys) && ys[next].first == y {
+			var row []rasterImagePixel
+			if n := len(free); n != 0 {
+				row, free = free[n-1], free[:n-1]
+				clear(row)
+			} else {
+				row = make([]rasterImagePixel, width)
+			}
+			active = append(active, rasterImageRow{sample: ys[next], values: row})
+			next++
+		}
+		rasterImageHorizontal(horizontal, pixels, xs, y, columns)
+		n := 0
+		for _, row := range active {
+			weight := row.sample.weights[y-row.sample.first]
+			if weight != 0 {
+				for x, value := range horizontal {
+					p := &row.values[x]
+					p.r += value.r * weight
+					p.g += value.g * weight
+					p.b += value.b * weight
+					p.a += value.a * weight
+				}
+			}
+			if y+1 == row.sample.first+len(row.sample.weights) {
+				rasterImageWriteRow(dst, output, row.values, xs[0].pixel, row.sample.pixel, op)
+				free = append(free, row.values)
+			} else {
+				active[n] = row
+				n++
+			}
+		}
+		active = active[:n]
+	}
+	return true
+}
+
+// rasterImageAxis 按连续源坐标生成CatmullRom权重，不对图像几何边界取整
+// 入参: first 目标起点, end 目标终点, source 源起点, limit 源终点, scale 缩放比例, offset 平移距离
+// 返回: []rasterAxisSample 轴向采样表
+func rasterImageAxis(first, end, source, limit int, scale, offset float64) []rasterAxisSample {
+	result := make([]rasterAxisSample, 0, end-first)
+	argument := math.Abs(scale)
+	support := draw.CatmullRom.Support / argument
+	for pixel := first; pixel < end; pixel++ {
+		center := (float64(pixel) + .5 - offset) / scale
+		if center < float64(source) || center >= float64(limit) {
+			continue
+		}
+		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)
+		total := 0.0
+		for i := range weights {
+			distance := math.Abs((float64(start+i) - center) * argument)
+			if distance < draw.CatmullRom.Support {
+				weights[i] = draw.CatmullRom.At(distance)
+				total += weights[i]
+			}
+		}
+		for i := range weights {
+			weights[i] /= total
+		}
+		result = append(result, rasterAxisSample{pixel: pixel, first: start, weights: weights})
+	}
+	return result
+}
+
+// rasterImageHorizontal 按源列复用像素，保留各目标像素的权重累加顺序与中间精度
+// 入参: row 横向缓冲, src 源像素, samples 采样表, y 源行坐标, columns 活动列缓冲
+func rasterImageHorizontal(row []rasterImagePixel, src image.RGBA64Image, samples []rasterAxisSample, y int, columns []int) {
+	clear(row)
+	reversed := samples[0].first > samples[len(samples)-1].first
+	start, end := samples[0].first, samples[0].first+len(samples[0].weights)
+	for _, sample := range samples[1:] {
+		start = min(start, sample.first)
+		end = max(end, sample.first+len(sample.weights))
+	}
+	next, count := 0, 0
+	for x := start; x < end; x++ {
+		for next < len(samples) {
+			index := next
+			if reversed {
+				index = len(samples) - next - 1
+			}
+			if samples[index].first > x {
+				break
+			}
+			columns[count] = index
+			count++
+			next++
+		}
+		p := src.RGBA64At(x, y)
+		n := 0
+		for _, index := range columns[:count] {
+			sample := samples[index]
+			weight := sample.weights[x-sample.first]
+			if weight != 0 {
+				value := &row[index]
+				value.r += float64(p.R) * weight
+				value.g += float64(p.G) * weight
+				value.b += float64(p.B) * weight
+				value.a += float64(p.A) * weight
+			}
+			if x+1 < sample.first+len(sample.weights) {
+				columns[n] = index
+				n++
+			}
+		}
+		count = n
+	}
+}
+
+// rasterImageWriteRow 在两轴采样完成后取整并使用标准预乘合成
+// 入参: dst 目标图像, output 行像素缓冲, values 累积颜色, x 横向起点, y 目标行坐标, op 合成操作
+func rasterImageWriteRow(dst draw.Image, output *image.RGBA64, values []rasterImagePixel, x, y int, op draw.Op) {
+	for i, value := range values {
+		output.SetRGBA64(i, 0, color.RGBA64{
+			R: uint16(min(max(min(value.r, value.a)+.5, 0), 65535)),
+			G: uint16(min(max(min(value.g, value.a)+.5, 0), 65535)),
+			B: uint16(min(max(min(value.b, value.a)+.5, 0), 65535)),
+			A: uint16(min(max(value.a+.5, 0), 65535)),
+		})
+	}
+	draw.Draw(dst, image.Rect(x, y, x+len(values), y+1), output, image.Point{}, op)
+}
+
+// DrawPixels 对轴向缩小使用可分离采样，其余变换保留通用路径
+// 入参: dst 目标图像, src 源图像, m 按a、b、c、d、e、f排列的像素变换, op 合成操作
+func DrawPixels(dst draw.Image, src image.Image, m [6]float64, op draw.Op) {
+	b := src.Bounds()
+	if dr, ok := rasterScaleBounds(b, m); ok {
+		if dr.Intersect(dst.Bounds()).Empty() {
+			return
+		}
+		draw.CatmullRom.Scale(dst, dr, src, b, op, nil)
+		return
+	}
+	if drawRasterAxisImage(dst, src, m, op) {
+		return
+	}
+	draw.CatmullRom.Transform(dst, f64.Aff3{m[0], m[2], m[4], m[1], m[3], m[5]}, src, b, op, nil)
+}
+
+// rasterScaleBounds 检查变换是否可无几何取整地使用缩放器，并限制其中间缓冲
+// 入参: b 源边界, m 像素变换
+// 返回: image.Rectangle 缩放边界, bool 是否适用
+func rasterScaleBounds(b image.Rectangle, m [6]float64) (image.Rectangle, bool) {
+	if b.Empty() || m[1] != 0 || m[2] != 0 || m[0] <= 0 || m[0] > 1 || m[3] <= 0 || m[3] > 1 || m[0] == 1 && m[3] == 1 {
+		return image.Rectangle{}, false
+	}
+	x0, y0 := float64(m[0]*float64(b.Min.X))+m[4], float64(m[3]*float64(b.Min.Y))+m[5]
+	x1, y1 := float64(m[0]*float64(b.Max.X))+m[4], float64(m[3]*float64(b.Max.Y))+m[5]
+	for _, v := range [4]float64{x0, y0, x1, y1} {
+		if v != math.Floor(v) || v < math.MinInt32 || v > math.MaxInt32 {
+			return image.Rectangle{}, false
+		}
+	}
+	if x1 <= x0 || y1 <= y0 || b.Dx() > math.MaxInt32 || b.Dy() > math.MaxInt32 || (x1-x0)*float64(b.Dy()) > rasterScaleBufferLimit/32 {
+		return image.Rectangle{}, false
+	}
+	return image.Rect(int(x0), int(y0), int(x1), int(y1)), true
+}
+
+// TransformBounds 计算采样器可能写入的像素范围，并在整数转换前裁至目标边界
+// 入参: source 原始像素边界, m 像素变换, target 目标边界
+// 返回: image.Rectangle 受影响的目标像素区域
+func TransformBounds(source image.Rectangle, m [6]float64, target image.Rectangle) image.Rectangle {
+	minX, minY, maxX, maxY := math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)
+	for _, p := range [4]image.Point{source.Min, {X: source.Max.X, Y: source.Min.Y}, {X: source.Min.X, Y: source.Max.Y}, source.Max} {
+		x := math.Floor(float64(m[0]*float64(p.X)) + float64(m[2]*float64(p.Y)) + m[4])
+		y := math.Floor(float64(m[1]*float64(p.X)) + float64(m[3]*float64(p.Y)) + m[5])
+		minX, minY = math.Min(minX, x), math.Min(minY, y)
+		maxX, maxY = math.Max(maxX, x+1), math.Max(maxY, y+1)
+	}
+	minX, minY = math.Max(minX, float64(target.Min.X)), math.Max(minY, float64(target.Min.Y))
+	maxX, maxY = math.Min(maxX, float64(target.Max.X)), math.Min(maxY, float64(target.Max.Y))
+	if minX >= maxX || minY >= maxY {
+		return image.Rectangle{}
+	}
+	return image.Rect(int(minX), int(minY), int(maxX), int(maxY))
+}