`rgba` — colors

RGBA is the color type used throughout cosh-tui. It stores an 8-bit-per- channel color plus an intent (how the color was specified) and an optional palette slot, so colors can round-trip between RGB, indexed (ANSI-256), and “terminal default” representations.

pub struct RGBA { /* r, g, b, a: u8, intent: ColorIntent, slot: u8 */ }

pub enum ColorIntent { Rgb, Indexed, Default }

Constructing colors

Constructor	Meaning
`from_ints(r, g, b, a)`	8-bit channels, `0..=255` each. `const`.
`from_values(r, g, b, a)`	Float channels, each clamped to `0.0..=1.0`.
`from_hex("#rrggbb" \| "#rrggbbaa")`	Hex string; also accepts 3- and 4-digit shorthand (`#rgb`, `#rgba`).
`from_index(index, snapshot)`	ANSI-256 index; `snapshot` optionally overrides the color map.
`default_foreground(snapshot)` / `default_background(snapshot)`	The terminal’s defaults.

Hex parsing quirks worth knowing:

A leading # is optional and stripped.
#abc expands to #aabbcc; #abcd expands to #aabbccdd.
Invalid input (bad length or non-hex digits) returns magenta RGBA::from_values(1.0, 0.0, 1.0, 1.0) — the classic “invalid color” sentinel — rather than failing.
rgb_to_hex(&RGBA) -> String produces #rrggbb (or #rrggbbaa when alpha ≠ 255).

Reading colors

to_ints() -> (u8, u8, u8, u8) — raw channels.
r() / g() / b() / a() -> f32 — normalized 0.0..=1.0.
map(f) -> (R, R, R, R) — apply a function to all four channels.
equals(other: Option<&Self>) -> bool — equality against an Option (handy for Option<RGBA> fields).
Display — prints rgba(0.50, 0.20, 0.10, 1.00).

Setters set_r/set_g/set_b/set_a(f32) mutate a channel, clamping to 0.0..=1.0.

ANSI-256 conversion

pub const fn ansi256_index_to_rgb(index: u8) -> RgbTriplet  // (u8, u8, u8)

Maps an ANSI-256 index (0–255) to its RGB triple: 0–15 are the ANSI-16 palette, 16–231 are the 6×6×6 color cube, 232–255 are the grayscale ramp. normalize_indexed_color_index(index) is the identity today but exists so the index can be normalized centrally.

`ColorInput` — where colors come from

Widgets accept colors as Option<ColorInput>:

pub enum ColorInput {
    String(String),   // "#ffcc00", "red", "transparent", …
    RGBA(RGBA),
}

From<&str> and From<RGBA> convert into ColorInput.
parse_color(ColorInput) -> RGBA resolves it: "transparent" → alpha 0, known CSS names → their hex, everything else → parsed as hex.
normalize_color_value(Option<ColorInput>) -> Option<NormalizedColorValue> parses an Option, keeping it wrapped.

Recognized CSS names include the 16 HTML colors, the extended set (silver, maroon, olive, lime, aqua, teal, navy, fuchsia, purple, orange, …) and bright* variants (brightred, brightgreen, …). Lookup is case-insensitive.

HSV

pub fn hsv_to_rgb(h: f32, s: f32, v: f32) -> RGBA

Standard HSV→RGB conversion (h in degrees) returning an opaque RGBA.

Example

use cosh_tui::core::lib::rgba::{RGBA, ColorInput, parse_color};

let a = RGBA::from_hex("#ff8800");            // opaque orange
let b = RGBA::from_ints(255, 136, 0, 255);
assert_eq!(a, b);

let named = parse_color(ColorInput::String("orange".into()));
assert_eq!(named, RGBA::from_hex("#ffa500"));

let transparent = parse_color(ColorInput::String("transparent".into()));
assert_eq!(transparent.to_ints(), (0, 0, 0, 0));

assert_eq!(RGBA::from_hex("#nope").to_ints(), (255, 0, 255, 255)); // magenta sentinel

Next: border — border characters and styles.

rgba — colors