✨ feat: color frames, derive grayscale frames at render time

src/frameformat.go

@@ -9,7 +9,7 @@ import (
 )
 
 // .tsf container, little-endian: "TSFR" | version uint16 | fps float64 |
-// count uint32 | count × (length uint32, JPEG bytes).
+// count uint32 | count × (colorLen uint32, color JPEG).
 const (
 	tsfMagic   = "TSFR"
 	tsfVersion = 1
@@ -29,13 +29,13 @@ func writeTSF(output string, data *FramesContainer) error {
 	var hdr [14]byte
 	binary.LittleEndian.PutUint16(hdr[0:], tsfVersion)
 	binary.LittleEndian.PutUint64(hdr[2:], math.Float64bits(data.FPS))
-	binary.LittleEndian.PutUint32(hdr[10:], uint32(len(data.Frames)))
+	binary.LittleEndian.PutUint32(hdr[10:], uint32(len(data.ColorFrames)))
 	if _, err := w.Write(hdr[:]); err != nil {
 		return err
 	}
 
 	var lenBuf [4]byte
-	for _, frame := range data.Frames {
+	for _, frame := range data.ColorFrames {
 		binary.LittleEndian.PutUint32(lenBuf[:], uint32(len(frame)))
 		if _, err := w.Write(lenBuf[:]); err != nil {
 			return err
@@ -66,7 +66,7 @@ func loadTSF(filename string) (*FramesContainer, error) {
 	fps := math.Float64frombits(binary.LittleEndian.Uint64(raw[6:]))
 	count := binary.LittleEndian.Uint32(raw[14:])
 
-	frames := make([][]byte, 0, count)
+	colorFrames := make([][]byte, 0, count)
 	off := 18
 	for range count {
 		if off+4 > len(raw) {
@@ -77,15 +77,15 @@ func loadTSF(filename string) (*FramesContainer, error) {
 		if off+n > len(raw) {
 			return nil, invalid()
 		}
-		frames = append(frames, raw[off:off+n])
+		colorFrames = append(colorFrames, raw[off:off+n])
 		off += n
 	}
 
-	if len(frames) == 0 || fps <= 0 {
+	if len(colorFrames) == 0 || fps <= 0 {
 		return nil, fmt.Errorf(
 			"invalid frames file %q: expected non-empty frames and a positive fps",
 			filename,
 		)
 	}
-	return &FramesContainer{Frames: frames, FPS: fps}, nil
+	return &FramesContainer{ColorFrames: colorFrames, FPS: fps}, nil
 }