1 files changed, 34 insertions, 3 deletions

diff --git a/internal/color/color.go b/internal/color/color.go
index 22fa143..13fca69 100644
--- a/internal/color/color.go
+++ b/internal/color/color.go
@@ -243,6 +243,24 @@ func NoColor() ColorSpec {
 	return ColorSpec{Fg: -1, Bg: -1}
 }
 
+// Average returns a ColorSpec whose foreground is the RGB midpoint of the two
+// inputs' foregrounds. If only one input has a foreground, that one is used; if
+// neither does, NoColor is returned. Styles and background are not carried over.
+func Average(a, b ColorSpec) ColorSpec {
+	if a.Fg < 0 && b.Fg < 0 {
+		return NoColor()
+	}
+	if a.Fg < 0 {
+		return ColorSpec{Fg: b.Fg, Bg: -1}
+	}
+	if b.Fg < 0 {
+		return ColorSpec{Fg: a.Fg, Bg: -1}
+	}
+	r1, g1, b1 := Xterm256ToRGB(a.Fg)
+	r2, g2, b2 := Xterm256ToRGB(b.Fg)
+	return ColorSpec{Fg: NearestXterm256((r1+r2)/2, (g1+g2)/2, (b1+b2)/2), Bg: -1}
+}
+
 func Parse(input string) ColorSpec {
 	spec := ColorSpec{Fg: -1, Bg: -1}
 	for _, token := range strings.Fields(input) {
@@ -254,14 +272,14 @@ func Parse(input string) ColorSpec {
 		case token == "underline":
 			spec.Underline = true
 		case strings.HasPrefix(token, "bg:"):
-			if n, err := strconv.Atoi(strings.TrimPrefix(token, "bg:")); err == nil && n >= 0 && n <= 255 {
+			if n, ok := parseColorIndex(strings.TrimPrefix(token, "bg:")); ok {
 				spec.Bg = n
 			}
 		case strings.HasPrefix(token, "g:"):
 			parts := strings.Split(token[2:], ",")
 			var stops []int
 			for _, p := range parts {
-				if n, err := strconv.Atoi(strings.TrimSpace(p)); err == nil && n >= 0 && n <= 255 {
+				if n, ok := parseColorIndex(strings.TrimSpace(p)); ok {
 					stops = append(stops, n)
 				}
 			}
@@ -269,7 +287,7 @@ func Parse(input string) ColorSpec {
 				spec.Gradient = stops
 			}
 		default:
-			if n, err := strconv.Atoi(token); err == nil && n >= 0 && n <= 255 {
+			if n, ok := parseColorIndex(token); ok {
 				spec.Fg = n
 			}
 		}
@@ -277,6 +295,19 @@ func Parse(input string) ColorSpec {
 	return spec
 }
 
+// parseColorIndex parses a 1-2 digit hexadecimal color index (00-FF, case
+// insensitive) into its 0-255 value. Out-of-range or non-hex input fails.
+func parseColorIndex(s string) (int, bool) {
+	if s == "" {
+		return 0, false
+	}
+	n, err := strconv.ParseUint(s, 16, 0)
+	if err != nil || n > 255 {
+		return 0, false
+	}
+	return int(n), true
+}
+
 func (s ColorSpec) Empty() bool {
 	return s.Fg < 0 && s.Bg < 0 && !s.Bold && !s.Dim && !s.Underline && len(s.Gradient) == 0
 }