fix: preserve color codes in STL

srt.go

@@ -179,7 +179,10 @@ func parseTextSrt(i string, sa *StyleAttributes) (o Line) {
 				sa.SRTUnderline = true
 			case "font":
 				if c := htmlTokenAttribute(&token, "color"); c != nil {
-					sa.SRTColor = c
+					// Parse the color string into a Color struct
+					if color, err := newColorFromHTMLString(*c); err == nil {
+						sa.SRTColor = color
+					}
 				}
 			}
 		case html.TextToken:
@@ -266,7 +269,7 @@ func (li LineItem) srtBytes() (c []byte) {
 	// Get color
 	var color string
 	if li.InlineStyle != nil && li.InlineStyle.SRTColor != nil {
-		color = *li.InlineStyle.SRTColor
+		color = li.InlineStyle.SRTColor.HTMLString()
 	}
 
 	// Get bold/italics/underline

srt_test.go

@@ -92,15 +92,15 @@ func TestSRTStyled(t *testing.T) {
 	assert.Equal(t, " = 100", s.Items[9].Lines[0].Items[3].Text)
 
 	// assert the styles of the items
-	assert.Equal(t, "#00ff00", *s.Items[0].Lines[0].Items[0].InlineStyle.SRTColor)
+	assert.Equal(t, astisub.ColorLime, s.Items[0].Lines[0].Items[0].InlineStyle.SRTColor)
 	assert.True(t, s.Items[0].Lines[0].Items[0].InlineStyle.SRTBold)
 	assert.False(t, s.Items[0].Lines[0].Items[0].InlineStyle.SRTItalics)
 	assert.False(t, s.Items[0].Lines[0].Items[0].InlineStyle.SRTUnderline)
-	assert.Equal(t, "#ff00ff", *s.Items[1].Lines[0].Items[0].InlineStyle.SRTColor)
+	assert.Equal(t, astisub.ColorMagenta, s.Items[1].Lines[0].Items[0].InlineStyle.SRTColor)
 	assert.False(t, s.Items[1].Lines[0].Items[0].InlineStyle.SRTBold)
 	assert.False(t, s.Items[1].Lines[0].Items[0].InlineStyle.SRTItalics)
 	assert.False(t, s.Items[1].Lines[0].Items[0].InlineStyle.SRTUnderline)
-	assert.Equal(t, "#00ff00", *s.Items[2].Lines[0].Items[0].InlineStyle.SRTColor)
+	assert.Equal(t, astisub.ColorLime, s.Items[2].Lines[0].Items[0].InlineStyle.SRTColor)
 	assert.False(t, s.Items[2].Lines[0].Items[0].InlineStyle.SRTBold)
 	assert.False(t, s.Items[2].Lines[0].Items[0].InlineStyle.SRTItalics)
 	assert.False(t, s.Items[2].Lines[0].Items[0].InlineStyle.SRTUnderline)

stl.go

@@ -729,6 +729,31 @@ func stlVerticalPositionFromStyle(sa *StyleAttributes) int {
 func (li LineItem) STLString() string {
 	rs := li.Text
 	if li.InlineStyle != nil {
+		// Add color code prefix
+		if li.InlineStyle.STLColor != nil {
+			var colorCode byte
+			switch li.InlineStyle.STLColor {
+			case ColorBlack:
+				colorCode = 0x00
+			case ColorRed:
+				colorCode = 0x01
+			case ColorGreen:
+				colorCode = 0x02
+			case ColorYellow:
+				colorCode = 0x03
+			case ColorBlue:
+				colorCode = 0x04
+			case ColorMagenta:
+				colorCode = 0x05
+			case ColorCyan:
+				colorCode = 0x06
+			case ColorWhite:
+				colorCode = 0x07
+			default:
+				colorCode = 0x07 // Default to white
+			}
+			rs = string(rune(colorCode)) + rs
+		}
 		if li.InlineStyle.STLItalics != nil && *li.InlineStyle.STLItalics {
 			rs = string(rune(0x80)) + rs + string(rune(0x81))
 		}
@@ -867,6 +892,7 @@ func (h *stlCharacterHandler) decode(i byte) (o []byte) {
 
 type stlStyler struct {
 	boxing    *bool
+	color     *Color
 	italics   *bool
 	underline *bool
 }
@@ -877,6 +903,22 @@ func newSTLStyler() *stlStyler {
 
 func (s *stlStyler) parseSpacingAttribute(i byte) {
 	switch i {
+	case 0x00:
+		s.color = ColorBlack
+	case 0x01:
+		s.color = ColorRed
+	case 0x02:
+		s.color = ColorGreen
+	case 0x03:
+		s.color = ColorYellow
+	case 0x04:
+		s.color = ColorBlue
+	case 0x05:
+		s.color = ColorMagenta
+	case 0x06:
+		s.color = ColorCyan
+	case 0x07:
+		s.color = ColorWhite
 	case 0x80:
 		s.italics = astikit.BoolPtr(true)
 	case 0x81:
@@ -893,11 +935,11 @@ func (s *stlStyler) parseSpacingAttribute(i byte) {
 }
 
 func (s *stlStyler) hasBeenSet() bool {
-	return s.italics != nil || s.boxing != nil || s.underline != nil
+	return s.italics != nil || s.boxing != nil || s.underline != nil || s.color != nil
 }
 
 func (s *stlStyler) hasChanged(sa *StyleAttributes) bool {
-	return s.boxing != sa.STLBoxing || s.italics != sa.STLItalics || s.underline != sa.STLUnderline
+	return s.boxing != sa.STLBoxing || s.italics != sa.STLItalics || s.underline != sa.STLUnderline || s.color != sa.STLColor
 }
 
 func (s *stlStyler) propagateStyleAttributes(sa *StyleAttributes) {
@@ -908,6 +950,9 @@ func (s *stlStyler) update(sa *StyleAttributes) {
 	if s.boxing != nil && s.boxing != sa.STLBoxing {
 		sa.STLBoxing = s.boxing
 	}
+	if s.color != nil && s.color != sa.STLColor {
+		sa.STLColor = s.color
+	}
 	if s.italics != nil && s.italics != sa.STLItalics {
 		sa.STLItalics = s.italics
 	}
@@ -1053,10 +1098,6 @@ func parseSTLJustificationCode(i byte) Justification {
 	}
 }
 
-func isTeletextControlCode(i byte) (b bool) {
-	return i <= 0x1f
-}
-
 func parseOpenSubtitleRow(i *Item, d decoder, fs func() styler, row []byte) error {
 	// Loop through columns
 	var l = Line{}
@@ -1068,14 +1109,22 @@ func parseOpenSubtitleRow(i *Item, d decoder, fs func() styler, row []byte) erro
 			s = fs()
 		}
 
-		if isTeletextControlCode(v) {
+		// Check if this is a valid control code (color or style codes)
+		isTeletextControlCode := v <= 0x1f
+		isColorCode := v >= 0x00 && v <= 0x07
+		isStyleCode := v >= 0x80 && v <= 0x85
+
+		// Error on teletext control codes that aren't color or style codes
+		if isTeletextControlCode && !isColorCode && !isStyleCode {
 			return errors.New("teletext control code in open text")
 		}
+
+		// Parse spacing attributes (color and style codes)
 		if s != nil {
 			s.parseSpacingAttribute(v)
 		}
 
-		// Style has been set
+		// Style has been set by a control code
 		if s != nil && s.hasBeenSet() {
 			// Style has changed
 			if s.hasChanged(li.InlineStyle) {
@@ -1090,10 +1139,12 @@ func parseOpenSubtitleRow(i *Item, d decoder, fs func() styler, row []byte) erro
 				}
 				s.update(li.InlineStyle)
 			}
-		} else {
-			// Append text
-			li.Text += string(d.decode(v))
+			// Control codes don't get appended as text, continue to next byte
+			continue
 		}
+
+		// Not a control code, append as text
+		li.Text += string(d.decode(v))
 	}
 
 	appendOpenSubtitleLineItem(&l, li, s)

stl_test.go

@@ -135,3 +135,178 @@ func TestTTMLToSTLGSIBlock(t *testing.T) {
 	assert.True(t, displayStandardCode == "0" || displayStandardCode == "1" || displayStandardCode == "2",
 		"Display standard code should be '0', '1', or '2', got '%s'", displayStandardCode)
 }
+
+func TestSTLColors(t *testing.T) {
+	// Create subtitles with different colored text
+	s := astisub.NewSubtitles()
+	s.Metadata = &astisub.Metadata{
+		Framerate:              25,
+		STLDisplayStandardCode: "0", // Open subtitling
+	}
+
+	// Add items with different colors
+	s.Items = []*astisub.Item{
+		{
+			StartAt: time.Second,
+			EndAt:   2 * time.Second,
+			Lines: []astisub.Line{
+				{
+					Items: []astisub.LineItem{
+						{
+							Text: "Red text",
+							InlineStyle: &astisub.StyleAttributes{
+								STLColor: astisub.ColorRed,
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			StartAt: 3 * time.Second,
+			EndAt:   4 * time.Second,
+			Lines: []astisub.Line{
+				{
+					Items: []astisub.LineItem{
+						{
+							Text: "Green text",
+							InlineStyle: &astisub.StyleAttributes{
+								STLColor: astisub.ColorGreen,
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			StartAt: 5 * time.Second,
+			EndAt:   6 * time.Second,
+			Lines: []astisub.Line{
+				{
+					Items: []astisub.LineItem{
+						{
+							Text: "Blue text",
+							InlineStyle: &astisub.StyleAttributes{
+								STLColor: astisub.ColorBlue,
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			StartAt: 7 * time.Second,
+			EndAt:   8 * time.Second,
+			Lines: []astisub.Line{
+				{
+					Items: []astisub.LineItem{
+						{
+							Text: "Yellow text",
+							InlineStyle: &astisub.StyleAttributes{
+								STLColor: astisub.ColorYellow,
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	// Write to STL
+	w := &bytes.Buffer{}
+	err := s.WriteToSTL(w)
+	assert.NoError(t, err)
+
+	// Read back from STL
+	s2, err := astisub.ReadFromSTL(bytes.NewReader(w.Bytes()), astisub.STLOptions{})
+	assert.NoError(t, err)
+
+	// Verify colors are preserved
+	assert.Equal(t, 4, len(s2.Items))
+	assert.Equal(t, astisub.ColorRed, s2.Items[0].Lines[0].Items[0].InlineStyle.STLColor)
+	assert.Equal(t, astisub.ColorGreen, s2.Items[1].Lines[0].Items[0].InlineStyle.STLColor)
+	assert.Equal(t, astisub.ColorBlue, s2.Items[2].Lines[0].Items[0].InlineStyle.STLColor)
+	assert.Equal(t, astisub.ColorYellow, s2.Items[3].Lines[0].Items[0].InlineStyle.STLColor)
+}
+
+func TestSTLColorsFromWebVTT(t *testing.T) {
+	// Open WebVTT file with colors
+	s, err := astisub.OpenFile("./testdata/example-out-styled.vtt")
+	assert.NoError(t, err)
+	assert.NotNil(t, s)
+
+	// Set metadata for STL
+	s.Metadata = &astisub.Metadata{
+		Framerate:              25,
+		STLDisplayStandardCode: "0", // Open subtitling
+	}
+
+	// Write to STL
+	w := &bytes.Buffer{}
+	err = s.WriteToSTL(w)
+	assert.NoError(t, err)
+
+	// Read back from STL
+	s2, err := astisub.ReadFromSTL(bytes.NewReader(w.Bytes()), astisub.STLOptions{})
+	assert.NoError(t, err)
+
+	// Verify colors are preserved through WebVTT -> STL -> STL round trip
+	// Item 1: lime color (maps to STLColor in WebVTT processing)
+	assert.Equal(t, 1, len(s2.Items[0].Lines))
+	if len(s2.Items[0].Lines[0].Items) > 0 {
+		assert.NotNil(t, s2.Items[0].Lines[0].Items[0].InlineStyle)
+		assert.NotNil(t, s2.Items[0].Lines[0].Items[0].InlineStyle.STLColor, "Item 1 should have STL color")
+	}
+
+	// Item 2: magenta color
+	assert.Equal(t, 1, len(s2.Items[1].Lines))
+	if len(s2.Items[1].Lines[0].Items) > 0 {
+		assert.NotNil(t, s2.Items[1].Lines[0].Items[0].InlineStyle)
+		assert.Equal(t, astisub.ColorMagenta, s2.Items[1].Lines[0].Items[0].InlineStyle.STLColor, "Item 2 should have magenta color")
+	}
+}
+
+func TestSTLColorsFromTTML(t *testing.T) {
+	// Open TTML file with colors
+	s, err := astisub.OpenFile("./testdata/example-in.ttml")
+	assert.NoError(t, err)
+	assert.NotNil(t, s)
+
+	// Set metadata for STL
+	s.Metadata = &astisub.Metadata{
+		Framerate:              25,
+		STLDisplayStandardCode: "0", // Open subtitling
+	}
+
+	// Write to STL
+	w := &bytes.Buffer{}
+	err = s.WriteToSTL(w)
+	assert.NoError(t, err)
+
+	// Read back from STL
+	s2, err := astisub.ReadFromSTL(bytes.NewReader(w.Bytes()), astisub.STLOptions{})
+	assert.NoError(t, err)
+
+	// Verify colors are preserved through TTML -> STL -> STL round trip
+	// Item 1: has black color in span
+	assert.Equal(t, 1, len(s2.Items[0].Lines))
+	if len(s2.Items[0].Lines[0].Items) > 0 {
+		assert.NotNil(t, s2.Items[0].Lines[0].Items[0].InlineStyle)
+		assert.Equal(t, astisub.ColorBlack, s2.Items[0].Lines[0].Items[0].InlineStyle.STLColor, "Item 1 should have black color")
+	}
+
+	// Item 2: has green color in one of the spans (across multiple lines due to <br/>)
+	foundGreen := false
+	for _, line := range s2.Items[1].Lines {
+		for _, item := range line.Items {
+			if item.InlineStyle != nil && item.InlineStyle.STLColor == astisub.ColorGreen {
+				foundGreen = true
+				break
+			}
+		}
+		if foundGreen {
+			break
+		}
+	}
+	assert.True(t, foundGreen, "Item 2 should have a span with green color")
+}