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//! Convert colors to and from the hex-color string format at runtime
//!
//! Supports the 3, 4, 6, and 8-digit formats, according to the specification in
//! <https://drafts.csswg.org/css-color-4/#hex-color>
use std::{fmt::Display, str::FromStr};
use crate::Color32;
#[repr(C)]
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
/// A wrapper around Color32 that converts to and from a hex-color string
///
/// Implements [`Display`] and [`FromStr`] to convert to and from the hex string.
pub enum HexColor {
/// 3 hexadecimal digits, one for each of the r, g, b channels
Hex3(Color32),
/// 4 hexadecimal digits, one for each of the r, g, b, a channels
Hex4(Color32),
/// 6 hexadecimal digits, two for each of the r, g, b channels
Hex6(Color32),
/// 8 hexadecimal digits, one for each of the r, g, b, a channels
Hex8(Color32),
}
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum ParseHexColorError {
MissingHash,
InvalidLength,
InvalidInt(std::num::ParseIntError),
}
impl FromStr for HexColor {
type Err = ParseHexColorError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
s.strip_prefix('#')
.ok_or(ParseHexColorError::MissingHash)
.and_then(Self::from_str_without_hash)
}
}
impl Display for HexColor {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::Hex3(color) => {
let [r, g, b, _] = color.to_srgba_unmultiplied().map(|u| u >> 4);
f.write_fmt(format_args!("#{r:x}{g:x}{b:x}"))
}
Self::Hex4(color) => {
let [r, g, b, a] = color.to_srgba_unmultiplied().map(|u| u >> 4);
f.write_fmt(format_args!("#{r:x}{g:x}{b:x}{a:x}"))
}
Self::Hex6(color) => {
let [r, g, b, _] = color.to_srgba_unmultiplied();
let u = u32::from_be_bytes([0, r, g, b]);
f.write_fmt(format_args!("#{u:06x}"))
}
Self::Hex8(color) => {
let [r, g, b, a] = color.to_srgba_unmultiplied();
let u = u32::from_be_bytes([r, g, b, a]);
f.write_fmt(format_args!("#{u:08x}"))
}
}
}
}
impl HexColor {
/// Retrieves the inner [`Color32`]
#[inline]
pub fn color(&self) -> Color32 {
match self {
Self::Hex3(color) | Self::Hex4(color) | Self::Hex6(color) | Self::Hex8(color) => *color,
}
}
/// Parses a string as a hex color without the leading `#` character
///
/// # Errors
/// Returns an error if the length of the string does not correspond to one of the standard
/// formats (3, 4, 6, or 8), or if it contains non-hex characters.
#[inline]
pub fn from_str_without_hash(s: &str) -> Result<Self, ParseHexColorError> {
match s.len() {
3 => {
let [r, gb] = u16::from_str_radix(s, 16)
.map_err(ParseHexColorError::InvalidInt)?
.to_be_bytes();
let [r, g, b] = [r, gb >> 4, gb & 0x0f].map(|u| (u << 4) | u);
Ok(Self::Hex3(Color32::from_rgb(r, g, b)))
}
4 => {
let [r_g, b_a] = u16::from_str_radix(s, 16)
.map_err(ParseHexColorError::InvalidInt)?
.to_be_bytes();
let [r, g, b, a] =
[r_g >> 4, r_g & 0x0f, b_a >> 4, b_a & 0x0f].map(|u| (u << 4) | u);
Ok(Self::Hex4(Color32::from_rgba_unmultiplied(r, g, b, a)))
}
6 => {
let [_, r, g, b] = u32::from_str_radix(s, 16)
.map_err(ParseHexColorError::InvalidInt)?
.to_be_bytes();
Ok(Self::Hex6(Color32::from_rgb(r, g, b)))
}
8 => {
let [r, g, b, a] = u32::from_str_radix(s, 16)
.map_err(ParseHexColorError::InvalidInt)?
.to_be_bytes();
Ok(Self::Hex8(Color32::from_rgba_unmultiplied(r, g, b, a)))
}
_ => Err(ParseHexColorError::InvalidLength)?,
}
}
}
impl Color32 {
/// Parses a color from a hex string.
///
/// Supports the 3, 4, 6, and 8-digit formats, according to the specification in
/// <https://drafts.csswg.org/css-color-4/#hex-color>
///
/// To parse hex colors from string literals with compile-time checking, use the macro
/// [`crate::hex_color!`] instead.
///
/// # Example
/// ```rust
/// use ecolor::Color32;
/// assert_eq!(Ok(Color32::RED), Color32::from_hex("#ff0000"));
/// assert_eq!(Ok(Color32::GREEN), Color32::from_hex("#00ff00ff"));
/// assert_eq!(Ok(Color32::BLUE), Color32::from_hex("#00f"));
/// assert_eq!(Ok(Color32::TRANSPARENT), Color32::from_hex("#0000"));
/// ```
///
/// # Errors
/// Returns an error if the string doesn't start with the hash `#` character, if the remaining
/// length does not correspond to one of the standard formats (3, 4, 6, or 8), if it contains
/// non-hex characters.
pub fn from_hex(hex: &str) -> Result<Self, ParseHexColorError> {
HexColor::from_str(hex).map(|h| h.color())
}
/// Formats the color as a hex string.
///
/// # Example
/// ```rust
/// use ecolor::Color32;
/// assert_eq!(Color32::RED.to_hex(), "#ff0000ff");
/// assert_eq!(Color32::GREEN.to_hex(), "#00ff00ff");
/// assert_eq!(Color32::BLUE.to_hex(), "#0000ffff");
/// assert_eq!(Color32::TRANSPARENT.to_hex(), "#00000000");
/// ```
///
/// Uses the 8-digit format described in <https://drafts.csswg.org/css-color-4/#hex-color>,
/// as that is the only format that is lossless.
/// For other formats, see [`HexColor`].
#[inline]
pub fn to_hex(&self) -> String {
HexColor::Hex8(*self).to_string()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn hex_string_formats() {
use Color32 as C;
use HexColor as H;
let cases = [
(H::Hex3(C::RED), "#f00"),
(H::Hex4(C::RED), "#f00f"),
(H::Hex6(C::RED), "#ff0000"),
(H::Hex8(C::RED), "#ff0000ff"),
(H::Hex3(C::GREEN), "#0f0"),
(H::Hex4(C::GREEN), "#0f0f"),
(H::Hex6(C::GREEN), "#00ff00"),
(H::Hex8(C::GREEN), "#00ff00ff"),
(H::Hex3(C::BLUE), "#00f"),
(H::Hex4(C::BLUE), "#00ff"),
(H::Hex6(C::BLUE), "#0000ff"),
(H::Hex8(C::BLUE), "#0000ffff"),
(H::Hex3(C::WHITE), "#fff"),
(H::Hex4(C::WHITE), "#ffff"),
(H::Hex6(C::WHITE), "#ffffff"),
(H::Hex8(C::WHITE), "#ffffffff"),
(H::Hex3(C::BLACK), "#000"),
(H::Hex4(C::BLACK), "#000f"),
(H::Hex6(C::BLACK), "#000000"),
(H::Hex8(C::BLACK), "#000000ff"),
(H::Hex4(C::TRANSPARENT), "#0000"),
(H::Hex8(C::TRANSPARENT), "#00000000"),
];
for (color, string) in cases {
assert_eq!(color.to_string(), string, "{color:?} <=> {string}");
assert_eq!(
H::from_str(string).unwrap(),
color,
"{color:?} <=> {string}"
);
}
}
#[test]
fn hex_string_round_trip() {
let cases = [
[0, 20, 30, 0],
[10, 0, 30, 40],
[10, 100, 200, 0],
[10, 100, 200, 100],
[10, 100, 200, 200],
[10, 100, 200, 255],
[10, 100, 200, 40],
[10, 20, 0, 255],
[10, 20, 30, 0],
[10, 20, 30, 255],
[10, 20, 30, 40],
];
for [r, g, b, a] in cases {
let color = Color32::from_rgba_unmultiplied(r, g, b, a);
assert_eq!(Color32::from_hex(color.to_hex().as_str()), Ok(color));
}
}
}