v0.2.0 16 colors, default colors, /dev/tty, bracketed paste, themed form controls

color.go

@@ -8,8 +8,27 @@ type ColorMode uint8
 const (
 	ColorMode256       ColorMode = iota // xterm-256 palette
 	ColorModeTrueColor                  // 24-bit RGB
+	ColorMode16                         // ANSI 16: SGR 30-37/90-97, 40-47/100-107
+	ColorModeNone                       // no color; attributes only
 )
 
+// paletteTo16 maps an xterm-256 palette index to the nearest ANSI 16 index:
+// the first 16 are themselves, the cube and the grey ramp go by their shade
+func paletteTo16(i uint8) uint8 {
+	switch {
+	case i < 16:
+		return i
+	case i >= 232:
+		v := 8 + 10*(i-232)
+		return color.RGBTo16(color.RGB{R: v, G: v, B: v})
+	}
+	r, g, b := color.CubeRGB256(i)
+	return color.RGBTo16(color.RGB{R: cubeLevel[r], G: cubeLevel[g], B: cubeLevel[b]})
+}
+
+// cubeLevel is the channel value of each xterm color cube step
+var cubeLevel = [6]uint8{0, 95, 135, 175, 215, 255}
+
 // WarmPalette256 delegates to the color package's lazily evaluated 256-color LUT builder.
 // Exists to preserve terminal API backwards-compatibility.
 func WarmPalette256() {