v0.1.0 minor blend updates, lazy LUT build, example added
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package main
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import (
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"context"
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"fmt"
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stdcolor "image/color"
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"math"
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"os"
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"os/signal"
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"strings"
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"time"
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"github.com/lixenwraith/color"
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)
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const reset = "\x1b[0m"
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// bg returns the SGR sequence for a 24-bit background.
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func bg(c color.RGB) string { return fmt.Sprintf("\x1b[48;2;%d;%d;%dm", c.R, c.G, c.B) }
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// fg returns the SGR sequence for a 24-bit foreground.
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func fg(c color.RGB) string { return fmt.Sprintf("\x1b[38;2;%d;%d;%dm", c.R, c.G, c.B) }
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// block renders n background-colored spaces as a swatch.
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func block(c color.RGB, n int) string { return bg(c) + strings.Repeat(" ", n) + reset }
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func showPalette() {
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fmt.Println("── Named palette ──")
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entries := []struct {
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name string
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c color.RGB
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}{
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{"Black", color.Black}, {"White", color.White}, {"Red", color.Red},
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{"Orange", color.Orange}, {"Gold", color.Gold}, {"Yellow", color.Yellow},
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{"Lime", color.Lime}, {"ForestGreen", color.ForestGreen}, {"Teal", color.Teal},
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{"Cyan", color.Cyan}, {"RoyalBlue", color.RoyalBlue}, {"Blue", color.Blue},
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{"Magenta", color.Magenta}, {"HotPink", color.HotPink}, {"Coral", color.Coral},
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{"Silver", color.Silver},
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}
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for _, e := range entries {
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fmt.Printf("%s %-12s %s\n", block(e.c, 4), e.name, e.c.Hex())
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}
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fmt.Println()
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}
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func showBlendModes() {
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fmt.Println("── Blend modes (dst=NavyBlue, src=Orange, alpha=0.6) ──")
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dst, src := color.NavyBlue, color.Orange
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const a = 0.6
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fmt.Printf("%s dst %s src\n", block(dst, 6), block(src, 6))
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modes := []struct {
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name string
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out color.RGB
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}{
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{"Blend", color.Blend(dst, src, a)},
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{"Add", color.Add(dst, src, a)},
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{"Screen", color.Screen(dst, src, a)},
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{"Overlay", color.Overlay(dst, src, a)},
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{"SoftLight", color.SoftLight(dst, src, a)},
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{"Max", color.Max(dst, src, a)},
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}
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for _, m := range modes {
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fmt.Printf("%s %-10s %s\n", block(m.out, 6), m.name, m.out.Hex())
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}
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fmt.Println()
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}
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func showGradient() {
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fmt.Println("── Lerp gradient: DarkCrimson → Gold → Teal ──")
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stops := []color.RGB{color.DarkCrimson, color.Gold, color.Teal}
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const steps = 36
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var line strings.Builder
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for i := 0; i < steps; i++ {
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seg := (float64(i) / float64(steps-1)) * float64(len(stops)-1)
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idx := int(seg)
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if idx >= len(stops)-1 {
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idx = len(stops) - 2
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}
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line.WriteString(block(color.Lerp(stops[idx], stops[idx+1], seg-float64(idx)), 1))
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}
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fmt.Println(line.String())
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fmt.Println()
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}
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func showGrayscale() {
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fmt.Println("── Grayscale, Desaturate, Luma ──")
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base := color.Coral
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fmt.Printf("%s base %s luma=%d\n", block(base, 6), base.Hex(), color.Luma(base))
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fmt.Printf("%s grayscale %s\n", block(color.Grayscale(base), 6), color.Grayscale(base).Hex())
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var line strings.Builder
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for i := 0; i <= 8; i++ {
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line.WriteString(block(color.Desaturate(base, float64(i)/8.0), 3))
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}
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fmt.Printf("%s desaturate t=0→1\n\n", line.String())
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}
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func showHex() {
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fmt.Println("── Hex parse / format ──")
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for _, s := range []string{"#ff8800", "0f0", "#1a1b26", "bad!"} {
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c, err := color.ParseHex(s)
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if err != nil {
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fmt.Printf(" %-8q → error: %v\n", s, err)
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continue
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}
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fmt.Printf(" %-8q → %s %s%s%s\n", s, block(c, 3), fg(c), c.Hex(), reset)
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}
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c := color.MustParseHex("#41c7c7")
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fmt.Printf(" MustParseHex(#41c7c7) → %s %s\n\n", block(c, 3), c.Hex())
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}
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func showNearest() {
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fmt.Println("── Nearest palette color (RedmeanDistance) ──")
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named := []struct {
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name string
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c color.RGB
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}{
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{"Red", color.Red}, {"Orange", color.Orange}, {"Gold", color.Gold},
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{"Lime", color.Lime}, {"Teal", color.Teal}, {"Blue", color.Blue},
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{"Magenta", color.Magenta}, {"White", color.White}, {"Black", color.Black},
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}
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for _, hex := range []string{"#ff5522", "#118ab2", "#2b2b2b"} {
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target := color.MustParseHex(hex)
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best, bestD := named[0], color.RedmeanDistance(target, named[0].c)
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for _, n := range named[1:] {
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if d := color.RedmeanDistance(target, n.c); d < bestD {
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best, bestD = n, d
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}
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}
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fmt.Printf(" %s %s ≈ %s %-8s %s\n", block(target, 3), hex, block(best.c, 3), best.name, best.c.Hex())
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}
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fmt.Println()
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}
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func showLerpFixed() {
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fmt.Println("── LerpFixed (Q16.16 fixed-point) ──")
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const shift = 16
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a, b := color.RoyalBlue, color.Gold
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var line strings.Builder
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for i := 0; i <= 16; i++ {
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t := int64(i) << (shift - 4) // i/16 expressed in Q16.16; spans [0, 1<<shift]
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line.WriteString(block(color.LerpFixed(a, b, t, shift), 3))
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}
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fmt.Printf("%s RoyalBlue → Gold\n\n", line.String())
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}
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func showImageBridge() {
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fmt.Println("── image/color bridge (From / RGBA) ──")
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// image/color values are alpha-premultiplied; From un-premultiplies and drops alpha.
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opaque := stdcolor.RGBA{R: 200, G: 100, B: 50, A: 255}
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c := color.From(opaque)
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fmt.Printf(" From(RGBA{200,100,50,255}) = %s %s\n", block(c, 3), c.Hex())
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half := stdcolor.RGBA{R: 100, G: 50, B: 25, A: 128} // 50%% alpha, premultiplied
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c2 := color.From(half)
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fmt.Printf(" From(50%% alpha) = %s %s (recovers base hue)\n", block(c2, 3), c2.Hex())
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var _ stdcolor.Color = color.Orange // RGB satisfies image/color.Color
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r, g, b, alpha := color.Orange.RGBA()
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fmt.Printf(" color.Orange.RGBA() = (%d,%d,%d,%d)\n\n", r, g, b, alpha)
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}
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// showPulse animates a Blend between two colors on one line until ctx is cancelled.
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func showPulse(ctx context.Context) {
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const width = 32
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fmt.Println("── Live pulse (Ctrl+C to exit) ──")
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base, glow := color.DodgerBlue, color.Gold
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ticker := time.NewTicker(60 * time.Millisecond)
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defer ticker.Stop()
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phase := 0.0
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for {
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select {
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case <-ctx.Done():
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fmt.Print("\r" + strings.Repeat(" ", width+10) + "\r")
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fmt.Println("interrupted — bye")
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return
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case <-ticker.C:
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phase += 0.15
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t := (math.Sin(phase) + 1) / 2 // 0..1
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fmt.Printf("\r%s t=%.2f", block(color.Blend(base, glow, t), width), t)
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}
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}
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}
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func main() {
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ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
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defer stop()
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showPalette()
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showBlendModes()
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showGradient()
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showGrayscale()
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showHex()
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showNearest()
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showLerpFixed()
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showImageBridge()
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showPulse(ctx)
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}
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