feat(字体图像): 优化字体图像与导出稳定性

internal/base/font/cff.go

@@ -1036,6 +1036,9 @@ func getCFFCharsetInfo(data []byte, numGlyphs int) ([]int, string, string, int,
 	if topDictData == nil {
 		return nil, "", "", 0, false
 	}
+	if _, _, _, err := scanCFFIndex(data, stringIndexOff); err != nil {
+		return nil, "", "", 0, false
+	}
 	td := parseCFFDict(topDictData)
 	registry, ordering := getCFFROS(data, stringIndexOff, td)
 	actual, err := parseCFFAndCountGlyphs(data)
@@ -1067,7 +1070,18 @@ func getCmapFromCFF(data []byte, numGlyphs int) map[rune]uint16 {
 	if !ok {
 		return nil
 	}
-	mapping := make(map[rune]uint16)
+	return cffCharsetMapping(data, sids, registry, ordering, stringIndexOff)
+}
+
+// cffCharsetMapping 根据已解析的CFF字符集恢复Unicode映射
+// 入参: data CFF数据, sids 字符标识, registry 注册机构, ordering 字符集, stringIndexOff 字符串索引偏移
+// 返回: map[rune]uint16 恢复的映射表
+func cffCharsetMapping(data []byte, sids []int, registry, ordering string, stringIndexOff int) map[rune]uint16 {
+	capacity := max(0, len(sids)-1)
+	if registry == "" || registry == "Adobe" && ordering == "GB1" {
+		capacity *= 2
+	}
+	mapping := make(map[rune]uint16, capacity)
 	if registry == "Adobe" && ordering == "GB1" {
 		for gid, cid := range sids {
 			if gid == 0 {
@@ -1100,7 +1114,7 @@ func getCmapFromCFF(data []byte, numGlyphs int) map[rune]uint16 {
 			}
 		} else {
 			idx := sid - 391
-			name = readStringIndexItem(data, stringIndexOff, idx)
+			name = string(readStringIndexItem(data, stringIndexOff, idx))
 		}
 		r := rune(0)
 		if name != "" {
@@ -1127,11 +1141,11 @@ func GetCFFCIDRuneMap(data []byte) map[uint16]rune {
 	if err != nil {
 		return nil
 	}
-	sids, registry, _, _, ok := getCFFCharsetInfo(cffData, numGlyphs)
+	sids, registry, ordering, stringIndexOff, ok := getCFFCharsetInfo(cffData, numGlyphs)
 	if !ok || registry == "" {
 		return nil
 	}
-	mapping := getCmapFromCFF(cffData, numGlyphs)
+	mapping := cffCharsetMapping(cffData, sids, registry, ordering, stringIndexOff)
 	if len(mapping) == 0 {
 		return nil
 	}
@@ -1187,7 +1201,7 @@ func getCFFData(data []byte) []byte {
 		}
 		offset := int(binary.BigEndian.Uint32(data[pos+8 : pos+12]))
 		length := int(binary.BigEndian.Uint32(data[pos+12 : pos+16]))
-		if offset < 0 || length < 0 || offset+length > len(data) {
+		if offset < 0 || length < 0 || offset > len(data) || length > len(data)-offset {
 			return nil
 		}
 		return data[offset : offset+length]
@@ -1269,31 +1283,29 @@ func parseCFFCharset(data []byte, offset, count int) ([]int, error) {
 
 // readStringIndexItem 读取CFF字符串索引项
 // 入参: data CFF数据, offset 索引偏移, idx 索引号
-// 返回: string 读取的字符串
-func readStringIndexItem(data []byte, offset int, idx int) string {
-	if offset >= len(data) {
-		return ""
+// 返回: []byte 共享原始数据的只读字符串，索引无效时为nil
+func readStringIndexItem(data []byte, offset int, idx int) []byte {
+	if offset < 0 || offset > len(data)-2 || idx < 0 {
+		return nil
 	}
 	count := int(binary.BigEndian.Uint16(data[offset:]))
+	if idx >= count || offset > len(data)-3 {
+		return nil
+	}
 	offSize := int(data[offset+2])
-	if idx >= count {
-		return ""
+	if offSize < 1 || offSize > 4 || count+1 > (len(data)-offset-3)/offSize {
+		return nil
 	}
 	offArrayStart := offset + 3
 	p1 := offArrayStart + idx*offSize
 	p2 := p1 + offSize
-	if p2+offSize > len(data) {
-		return ""
-	}
 	loc1 := readCFFOffset(data, p1, offSize)
 	loc2 := readCFFOffset(data, p2, offSize)
 	dataStart := offArrayStart + (count+1)*offSize
-	start := dataStart + loc1 - 1
-	length := loc2 - loc1
-	if start < 0 || start+length > len(data) {
-		return ""
+	if loc1 < 1 || loc2 < loc1 || loc2-1 > len(data)-dataStart {
+		return nil
 	}
-	return string(data[start : start+length])
+	return data[dataStart+loc1-1 : dataStart+loc2-1]
 }
 
 // getCFFROS 读取CID字体ROS信息
@@ -1317,7 +1329,7 @@ func getCFFSIDString(data []byte, stringIndexOff int, sid int) string {
 		return cffStandardStrings[sid]
 	}
 	if sid > 390 {
-		return readStringIndexItem(data, stringIndexOff, sid-391)
+		return string(readStringIndexItem(data, stringIndexOff, sid-391))
 	}
 	return ""
 }

internal/base/geom/arc.go

@@ -116,7 +116,7 @@ func centerArc(start Point, arc Segment) (geometryArc, error) {
 	}
 	angle := math.Mod(arc.Rotation, 360) * math.Pi / 180
 	sine, cosine := math.Sincos(angle)
-	dx, dy := (start.X-arc.End.X)/2, (start.Y-arc.End.Y)/2
+	dx, dy := arcCoordinateMean(start.X, -arc.End.X), arcCoordinateMean(start.Y, -arc.End.Y)
 	x, y := cosine*dx+sine*dy, -sine*dx+cosine*dy
 	scale := math.Hypot(x/rx, y/ry)
 	if scale > 1 {
@@ -139,13 +139,24 @@ func centerArc(start Point, arc Segment) (geometryArc, error) {
 	if !arc.Sweep && delta > 0 {
 		delta -= 2 * math.Pi
 	}
-	center := Point{cosine*cx - sine*cy + (start.X+arc.End.X)/2, sine*cx + cosine*cy + (start.Y+arc.End.Y)/2}
+	center := Point{cosine*cx - sine*cy + arcCoordinateMean(start.X, arc.End.X), sine*cx + cosine*cy + arcCoordinateMean(start.Y, arc.End.Y)}
 	if !finite(center.X) || !finite(center.Y) || !finite(rx) || !finite(ry) || !finite(delta) || !finite(theta) || delta == 0 {
 		return geometryArc{}, fmt.Errorf("invalid arc extent")
 	}
 	return geometryArc{center, Point{rx * cosine, rx * sine}, Point{-ry * sine, ry * cosine}, theta, delta}, nil
 }
 
+// arcCoordinateMean 计算有限坐标均值，仅在求和溢出时先减半，避免微小坐标提前下溢
+// 入参: a 第一个坐标, b 第二个坐标
+// 返回: float64 坐标均值
+func arcCoordinateMean(a, b float64) float64 {
+	value := (a + b) / 2
+	if math.IsInf(value, 0) {
+		return a/2 + b/2
+	}
+	return value
+}
+
 // point 计算椭圆参数对应的坐标
 // 入参: angle 参数角
 // 返回: Point 椭圆上的点

internal/base/geom/matrix.go

@@ -125,7 +125,7 @@ func (m Matrix) Invert() (Matrix, bool) {
 	return n, true
 }
 
-// matrixProductDifference 计算两个乘积之差，检查溢出、下溢及相消造成的精度损失
+// matrixProductDifference 补偿乘积相减的舍入残差，检查溢出、下溢及严重相消
 // 入参: a 第一个乘数, b 第二个乘数, c 第三个乘数, d 第四个乘数
 // 返回: float64 乘积之差, bool 是否可直接用于求逆
 func matrixProductDifference(a, b, c, d float64) (float64, bool) {
@@ -134,6 +134,9 @@ func matrixProductDifference(a, b, c, d float64) (float64, bool) {
 	if !finite(value) || x == 0 && a != 0 && b != 0 || y == 0 && c != 0 && d != 0 {
 		return value, false
 	}
+	if x != 0 && y != 0 {
+		value = math.FMA(a, b, -y) + math.FMA(-c, d, y)
+	}
 	return value, x == 0 && y == 0 || math.Abs(value) >= 0x1p-1022 && math.Abs(value) >= 0x1p-48*math.Max(math.Abs(x), math.Abs(y))
 }
 
@@ -169,7 +172,7 @@ func TranslationMatrix(x, y float64) Matrix {
 // YScale 获取Y轴缩放比例
 // 返回: float64 缩放比例
 func (m Matrix) YScale() float64 {
-	return math.Sqrt(m.c*m.c + m.d*m.d)
+	return math.Hypot(m.c, m.d)
 }
 
 // Equal 比较毫米坐标，使用固定绝对误差，不受绘图库全局精度影响

internal/base/geom/transform.go

@@ -33,10 +33,7 @@ func (p Path) Transform(matrix Matrix) (Path, error) {
 		}
 	}
 	matrixScale := math.Max(math.Max(math.Abs(matrix.a), math.Abs(matrix.b)), math.Max(math.Abs(matrix.c), math.Abs(matrix.d)))
-	determinant := 0.0
-	if matrixScale != 0 {
-		determinant = (matrix.a/matrixScale)*(matrix.d/matrixScale) - (matrix.b/matrixScale)*(matrix.c/matrixScale)
-	}
+	determinant, _ := matrixProductSum(matrix.a, matrix.d, -matrix.b, matrix.c)
 	transform := func(p Point) Point {
 		x, y := matrix.Transform(p.X, p.Y)
 		return Point{x, y}

internal/base/image/image.go

@@ -451,13 +451,11 @@ func GrayAt(img image.Image, x, y int) color.Gray {
 	case *colorImage:
 		return GrayAt(src.source, x, y)
 	case *maskedTIFFImage:
-		if src.NRGBA64At(x, y).A == 0 {
+		if src.alphaAt(x, y) == 0 {
 			return color.Gray{}
 		}
-		bounds, size := src.source.Bounds(), src.bounds.Size()
-		sx := bounds.Min.X + int((uint64(x-src.bounds.Min.X)*uint64(bounds.Dx())+uint64(bounds.Dx()/2))/uint64(size.X))
-		sy := bounds.Min.Y + int((uint64(y-src.bounds.Min.Y)*uint64(bounds.Dy())+uint64(bounds.Dy()/2))/uint64(size.Y))
-		return GrayAt(src.source, sx, sy)
+		point := src.samplePoint(src.source.Bounds(), x, y)
+		return GrayAt(src.source, point.X, point.Y)
 	case *transparentEdgeImage:
 		if x <= src.rect.Min.X || y <= src.rect.Min.Y || x >= src.rect.Max.X-1 || y >= src.rect.Max.Y-1 {
 			return color.Gray{}
@@ -534,6 +532,39 @@ func NRGBAAt(img image.Image, x, y int) color.NRGBA {
 // 返回: uint32 十六位透明度
 func AlphaAt(img image.Image, x, y int) uint32 {
 	switch source := img.(type) {
+	case *maskedTIFFImage:
+		return source.alphaAt(x, y)
+	case *image.YCbCr, *image.CMYK, *image.Gray, *image.Gray16:
+		return 65535
+	case *image.NYCbCrA:
+		if !image.Pt(x, y).In(source.Rect) {
+			return 0
+		}
+		return uint32(source.A[source.AOffset(x, y)]) * 257
+	case *orientedTIFFImage:
+		point, ok := source.sourcePoint(x, y)
+		if !ok {
+			return 0
+		}
+		return AlphaAt(source.source, point.X, point.Y)
+	case *planarTIFFImage:
+		if !image.Pt(x, y).In(source.bounds) {
+			return 0
+		}
+		if source.alpha != 0 {
+			index := 3
+			if source.cmyk {
+				index = 4
+			} else if source.gray || len(source.palette) != 0 {
+				index = 1
+			}
+			return uint32(source.sampleAt(index, x, y))
+		}
+		if len(source.palette) != 0 {
+			index := uint32(source.sampleAt(0, x, y)) * uint32(len(source.palette)-1) / 65535
+			return uint32(source.palette[index].A)
+		}
+		return 65535
 	case *image.RGBA:
 		if !(image.Point{X: x, Y: y}).In(source.Rect) {
 			return 0

internal/base/image/tiff_mask.go

@@ -49,6 +49,36 @@ func (s *maskedTIFFImage) Bounds() image.Rectangle { return s.bounds }
 // 返回: color.Model 颜色模型
 func (s *maskedTIFFImage) ColorModel() color.Model { return color.NRGBA64Model }
 
+// samplePoint 将显示坐标映射到主图或蒙版的像素中心
+// 入参: bounds 采样图像范围, x 横坐标, y 纵坐标
+// 返回: image.Point 采样坐标
+func (s *maskedTIFFImage) samplePoint(bounds image.Rectangle, x, y int) image.Point {
+	size := s.bounds.Size()
+	x, y = x-s.bounds.Min.X, y-s.bounds.Min.Y
+	if bounds.Size() == size {
+		return bounds.Min.Add(image.Pt(x, y))
+	}
+	return image.Pt(
+		bounds.Min.X+int((uint64(x)*uint64(bounds.Dx())+uint64(bounds.Dx()/2))/uint64(size.X)),
+		bounds.Min.Y+int((uint64(y)*uint64(bounds.Dy())+uint64(bounds.Dy()/2))/uint64(size.Y)),
+	)
+}
+
+// alphaAt 读取蒙版与主图透明度，不解算主图颜色
+// 入参: x 横坐标, y 纵坐标
+// 返回: uint32 十六位透明度
+func (s *maskedTIFFImage) alphaAt(x, y int) uint32 {
+	if !image.Pt(x, y).In(s.bounds) {
+		return 0
+	}
+	mask := s.samplePoint(s.mask.Bounds(), x, y)
+	if NRGBA64At(s.mask, mask.X, mask.Y).R == 0 {
+		return 0
+	}
+	source := s.samplePoint(s.source.Bounds(), x, y)
+	return AlphaAt(s.source, source.X, source.Y)
+}
+
 // NRGBA64At 按像素中心读取主图及蒙版，零位隐藏原图并保留隐藏颜色
 // 入参: x 横坐标, y 纵坐标
 // 返回: color.NRGBA64 非预乘十六位颜色
@@ -56,16 +86,10 @@ func (s *maskedTIFFImage) NRGBA64At(x, y int) color.NRGBA64 {
 	if !image.Pt(x, y).In(s.bounds) {
 		return color.NRGBA64{}
 	}
-	size := s.bounds.Size()
-	x, y = x-s.bounds.Min.X, y-s.bounds.Min.Y
-	b := s.source.Bounds()
-	sx := b.Min.X + int((uint64(x)*uint64(b.Dx())+uint64(b.Dx()/2))/uint64(size.X))
-	sy := b.Min.Y + int((uint64(y)*uint64(b.Dy())+uint64(b.Dy()/2))/uint64(size.Y))
-	pixel := NRGBA64At(s.source, sx, sy)
-	b = s.mask.Bounds()
-	mx := b.Min.X + int((uint64(x)*uint64(b.Dx())+uint64(b.Dx()/2))/uint64(size.X))
-	my := b.Min.Y + int((uint64(y)*uint64(b.Dy())+uint64(b.Dy()/2))/uint64(size.Y))
-	if NRGBA64At(s.mask, mx, my).R == 0 {
+	source := s.samplePoint(s.source.Bounds(), x, y)
+	pixel := NRGBA64At(s.source, source.X, source.Y)
+	mask := s.samplePoint(s.mask.Bounds(), x, y)
+	if NRGBA64At(s.mask, mask.X, mask.Y).R == 0 {
 		pixel.A = 0
 	}
 	return pixel