profile.go

package colorprofile

import (
	"image/color"
	"math"

	"github.com/charmbracelet/x/ansi"
	"github.com/lucasb-eyer/go-colorful"
)

// Profile is a color profile: NoTTY, Ascii, ANSI, ANSI256, or TrueColor.
type Profile byte

const (
	// NoTTY, not a terminal profile.
	NoTTY Profile = iota
	// Ascii, uncolored profile.
	Ascii //nolint:revive
	// ANSI, 4-bit color profile.
	ANSI
	// ANSI256, 8-bit color profile.
	ANSI256
	// TrueColor, 24-bit color profile.
	TrueColor
)

// String returns the string representation of a Profile.
func (p Profile) String() string {
	switch p {
	case TrueColor:
		return "TrueColor"
	case ANSI256:
		return "ANSI256"
	case ANSI:
		return "ANSI"
	case Ascii:
		return "Ascii"
	case NoTTY:
		return "NoTTY"
	}
	return "Unknown"
}

// Convert transforms a given Color to a Color supported within the Profile.
func (p Profile) Convert(c color.Color) color.Color {
	if p <= Ascii {
		return nil
	}

	switch c := c.(type) {
	case ansi.BasicColor:
		return c

	case ansi.ExtendedColor:
		if p == ANSI {
			return ansi256ToANSIColor(c)
		}
		return c

	case ansi.TrueColor, color.Color:
		h, ok := colorful.MakeColor(c)
		if !ok {
			return nil
		}
		if p != TrueColor {
			ac := hexToANSI256Color(h)
			if p == ANSI {
				return ansi256ToANSIColor(ac)
			}
			return ac
		}
		return c
	}

	return c
}

func hexToANSI256Color(c colorful.Color) ansi.ExtendedColor {
	v2ci := func(v float64) int {
		if v < 48 {
			return 0
		}
		if v < 115 {
			return 1
		}
		return int((v - 35) / 40)
	}

	// Calculate the nearest 0-based color index at 16..231
	r := v2ci(c.R * 255.0) // 0..5 each
	g := v2ci(c.G * 255.0)
	b := v2ci(c.B * 255.0)
	ci := 36*r + 6*g + b /* 0..215 */

	// Calculate the represented colors back from the index
	i2cv := [6]int{0, 0x5f, 0x87, 0xaf, 0xd7, 0xff}
	cr := i2cv[r] // r/g/b, 0..255 each
	cg := i2cv[g]
	cb := i2cv[b]

	// Calculate the nearest 0-based gray index at 232..255
	var grayIdx int
	average := (cr + cg + cb) / 3
	if average > 238 {
		grayIdx = 23
	} else {
		grayIdx = (average - 3) / 10 // 0..23
	}
	gv := 8 + 10*grayIdx // same value for r/g/b, 0..255

	// Return the one which is nearer to the original input rgb value
	c2 := colorful.Color{R: float64(cr) / 255.0, G: float64(cg) / 255.0, B: float64(cb) / 255.0}
	g2 := colorful.Color{R: float64(gv) / 255.0, G: float64(gv) / 255.0, B: float64(gv) / 255.0}
	colorDist := c.DistanceHSLuv(c2)
	grayDist := c.DistanceHSLuv(g2)

	if colorDist <= grayDist {
		return ansi.ExtendedColor(16 + ci) //nolint:gosec
	}
	return ansi.ExtendedColor(232 + grayIdx) //nolint:gosec
}

func ansi256ToANSIColor(c ansi.ExtendedColor) ansi.BasicColor {
	var r int
	md := math.MaxFloat64

	h, _ := colorful.Hex(ansiHex[c])
	for i := 0; i <= 15; i++ {
		hb, _ := colorful.Hex(ansiHex[i])
		d := h.DistanceHSLuv(hb)

		if d < md {
			md = d
			r = i
		}
	}

	return ansi.BasicColor(r) //nolint:gosec
}

// RGB values of ANSI colors (0-255).
var ansiHex = []string{
	"#000000",
	"#800000",
	"#008000",
	"#808000",
	"#000080",
	"#800080",
	"#008080",
	"#c0c0c0",
	"#808080",
	"#ff0000",
	"#00ff00",
	"#ffff00",
	"#0000ff",
	"#ff00ff",
	"#00ffff",
	"#ffffff",
	"#000000",
	"#00005f",
	"#000087",
	"#0000af",
	"#0000d7",
	"#0000ff",
	"#005f00",
	"#005f5f",
	"#005f87",
	"#005faf",
	"#005fd7",
	"#005fff",
	"#008700",
	"#00875f",
	"#008787",
	"#0087af",
	"#0087d7",
	"#0087ff",
	"#00af00",
	"#00af5f",
	"#00af87",
	"#00afaf",
	"#00afd7",
	"#00afff",
	"#00d700",
	"#00d75f",
	"#00d787",
	"#00d7af",
	"#00d7d7",
	"#00d7ff",
	"#00ff00",
	"#00ff5f",
	"#00ff87",
	"#00ffaf",
	"#00ffd7",
	"#00ffff",
	"#5f0000",
	"#5f005f",
	"#5f0087",
	"#5f00af",
	"#5f00d7",
	"#5f00ff",
	"#5f5f00",
	"#5f5f5f",
	"#5f5f87",
	"#5f5faf",
	"#5f5fd7",
	"#5f5fff",
	"#5f8700",
	"#5f875f",
	"#5f8787",
	"#5f87af",
	"#5f87d7",
	"#5f87ff",
	"#5faf00",
	"#5faf5f",
	"#5faf87",
	"#5fafaf",
	"#5fafd7",
	"#5fafff",
	"#5fd700",
	"#5fd75f",
	"#5fd787",
	"#5fd7af",
	"#5fd7d7",
	"#5fd7ff",
	"#5fff00",
	"#5fff5f",
	"#5fff87",
	"#5fffaf",
	"#5fffd7",
	"#5fffff",
	"#870000",
	"#87005f",
	"#870087",
	"#8700af",
	"#8700d7",
	"#8700ff",
	"#875f00",
	"#875f5f",
	"#875f87",
	"#875faf",
	"#875fd7",
	"#875fff",
	"#878700",
	"#87875f",
	"#878787",
	"#8787af",
	"#8787d7",
	"#8787ff",
	"#87af00",
	"#87af5f",
	"#87af87",
	"#87afaf",
	"#87afd7",
	"#87afff",
	"#87d700",
	"#87d75f",
	"#87d787",
	"#87d7af",
	"#87d7d7",
	"#87d7ff",
	"#87ff00",
	"#87ff5f",
	"#87ff87",
	"#87ffaf",
	"#87ffd7",
	"#87ffff",
	"#af0000",
	"#af005f",
	"#af0087",
	"#af00af",
	"#af00d7",
	"#af00ff",
	"#af5f00",
	"#af5f5f",
	"#af5f87",
	"#af5faf",
	"#af5fd7",
	"#af5fff",
	"#af8700",
	"#af875f",
	"#af8787",
	"#af87af",
	"#af87d7",
	"#af87ff",
	"#afaf00",
	"#afaf5f",
	"#afaf87",
	"#afafaf",
	"#afafd7",
	"#afafff",
	"#afd700",
	"#afd75f",
	"#afd787",
	"#afd7af",
	"#afd7d7",
	"#afd7ff",
	"#afff00",
	"#afff5f",
	"#afff87",
	"#afffaf",
	"#afffd7",
	"#afffff",
	"#d70000",
	"#d7005f",
	"#d70087",
	"#d700af",
	"#d700d7",
	"#d700ff",
	"#d75f00",
	"#d75f5f",
	"#d75f87",
	"#d75faf",
	"#d75fd7",
	"#d75fff",
	"#d78700",
	"#d7875f",
	"#d78787",
	"#d787af",
	"#d787d7",
	"#d787ff",
	"#d7af00",
	"#d7af5f",
	"#d7af87",
	"#d7afaf",
	"#d7afd7",
	"#d7afff",
	"#d7d700",
	"#d7d75f",
	"#d7d787",
	"#d7d7af",
	"#d7d7d7",
	"#d7d7ff",
	"#d7ff00",
	"#d7ff5f",
	"#d7ff87",
	"#d7ffaf",
	"#d7ffd7",
	"#d7ffff",
	"#ff0000",
	"#ff005f",
	"#ff0087",
	"#ff00af",
	"#ff00d7",
	"#ff00ff",
	"#ff5f00",
	"#ff5f5f",
	"#ff5f87",
	"#ff5faf",
	"#ff5fd7",
	"#ff5fff",
	"#ff8700",
	"#ff875f",
	"#ff8787",
	"#ff87af",
	"#ff87d7",
	"#ff87ff",
	"#ffaf00",
	"#ffaf5f",
	"#ffaf87",
	"#ffafaf",
	"#ffafd7",
	"#ffafff",
	"#ffd700",
	"#ffd75f",
	"#ffd787",
	"#ffd7af",
	"#ffd7d7",
	"#ffd7ff",
	"#ffff00",
	"#ffff5f",
	"#ffff87",
	"#ffffaf",
	"#ffffd7",
	"#ffffff",
	"#080808",
	"#121212",
	"#1c1c1c",
	"#262626",
	"#303030",
	"#3a3a3a",
	"#444444",
	"#4e4e4e",
	"#585858",
	"#626262",
	"#6c6c6c",
	"#767676",
	"#808080",
	"#8a8a8a",
	"#949494",
	"#9e9e9e",
	"#a8a8a8",
	"#b2b2b2",
	"#bcbcbc",
	"#c6c6c6",
	"#d0d0d0",
	"#dadada",
	"#e4e4e4",
	"#eeeeee",
}