Drop ASS tags that don't ever have a visible color

README.md

@@ -22,4 +22,9 @@ $ ffmpeg -y \
 -c:a copy \
 -c:s copy -disposition:s:0 forced -metadata:s:s:0 language=und \
 -shortest "${FILENAME}.mkv"
+```
+
+### Compress subtitles
+```bash
+zstd -19 -T24 file.ass -o file.ass.zst
 ```

ass/Renderer.go

@@ -3,6 +3,7 @@ package ass
 import (
 	"fmt"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/ass/line"
+	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/ass/tag"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/settings"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types/math"
@@ -167,6 +168,19 @@ func threadedRenderer(stats map[uint16]rendererStatsEntry, buf []*line.EventLine
 					break
 				}
 				l := buf[i]
+				var hasColor bool
+				for _, t := range l.Tags {
+					if ct, ok := t.(tag.ColorTag); ok && ct.HasColor() {
+						hasColor = true
+						break
+					}
+				}
+
+				if !hasColor {
+					//skip lines without any color at all
+					continue
+				}
+
 				stats[l.ObjectId].Lines.Add(1)
 
 				l.Name += fmt.Sprintf(" f:%d>%d~%d", l.Start, l.End, l.End-l.Start+1)

ass/tag/ContainerTag.go

@@ -18,6 +18,26 @@ type ContainerTag struct {
 	BakeTransforms *math.MatrixTransform
 }
 
+func (t *ContainerTag) HasColor() bool {
+	for _, tag := range t.Tags {
+		if colorTag, ok := tag.(ColorTag); ok {
+			if colorTag.HasColor() {
+				return true
+			}
+		}
+	}
+	for _, tags := range t.Transitions {
+		for _, tag := range tags {
+			if colorTag, ok := tag.(ColorTag); ok {
+				if colorTag.HasColor() {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
 func (t *ContainerTag) TransitionColor(event Event, transform math.ColorTransform) ColorTag {
 	container := t.Clone(false)
 

ass/tag/FillColorTag.go

@@ -5,6 +5,7 @@ import (
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/ass/time"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types/math"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types/shapes"
+	math2 "math"
 )
 
 type FillColorTag struct {
@@ -33,6 +34,10 @@ func (t *FillColorTag) TransitionStyleRecord(event Event, record shapes.StyleRec
 	return t2
 }
 
+func (t *FillColorTag) HasColor() bool {
+	return t.Color != nil && t.Color.Alpha > 0
+}
+
 func (t *FillColorTag) ApplyColorTransform(transform math.ColorTransform) ColorTag {
 	color := t.Color
 	if t.OriginalColor != nil {
@@ -60,6 +65,6 @@ func (t *FillColorTag) Encode(event time.EventTime) string {
 	if t.Color == nil {
 		return "\\1a&HFF&"
 	} else {
-		return fmt.Sprintf("\\1c&H%02X%02X%02X&\\1a&H%02X&", t.Color.B, t.Color.G, t.Color.R, 255-t.Color.Alpha)
+		return fmt.Sprintf("\\1c&H%02X%02X%02X&\\1a&H%02X&", t.Color.B, t.Color.G, t.Color.R, math2.MaxUint8-t.Color.Alpha)
 	}
 }

ass/tag/LineColorTag.go

@@ -5,6 +5,7 @@ import (
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/ass/time"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types/math"
 	"git.gammaspectra.live/WeebDataHoarder/swf2ass-go/types/shapes"
+	math2 "math"
 )
 
 type LineColorTag struct {
@@ -32,6 +33,10 @@ func (t *LineColorTag) TransitionStyleRecord(event Event, record shapes.StyleRec
 	return t2
 }
 
+func (t *LineColorTag) HasColor() bool {
+	return t.Color != nil && t.Color.Alpha > 0
+}
+
 func (t *LineColorTag) ApplyColorTransform(transform math.ColorTransform) ColorTag {
 	color := t.Color
 	if t.OriginalColor != nil {
@@ -59,6 +64,6 @@ func (t *LineColorTag) Encode(event time.EventTime) string {
 	if t.Color == nil {
 		return "\\3a&HFF&"
 	} else {
-		return fmt.Sprintf("\\3c&H%02X%02X%02X&\\3a&H%02X&", t.Color.B, t.Color.G, t.Color.R, 255-t.Color.Alpha)
+		return fmt.Sprintf("\\3c&H%02X%02X%02X&\\3a&H%02X&", t.Color.B, t.Color.G, t.Color.R, math2.MaxUint8-t.Color.Alpha)
 	}
 }

ass/tag/tag.go

@@ -42,4 +42,5 @@ type ColorTag interface {
 	StyleTag
 	ApplyColorTransform(transform math.ColorTransform) ColorTag
 	TransitionColor(event Event, transform math.ColorTransform) ColorTag
+	HasColor() bool
 }