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//! Conversion from Typst data types into CSS data types.
use std::fmt::{self, Display};
use typst_library::layout::Length;
use typst_library::visualize::{Color, Hsl, LinearRgb, Oklab, Oklch, Rgb};
use typst_utils::Numeric;
pub fn length(length: Length) -> impl Display {
typst_utils::display(move |f| match (length.abs.is_zero(), length.em.is_zero()) {
(false, false) => {
write!(f, "calc({}pt + {}em)", length.abs.to_pt(), length.em.get())
}
(true, false) => write!(f, "{}em", length.em.get()),
(_, true) => write!(f, "{}pt", length.abs.to_pt()),
})
}
pub fn color(color: Color) -> impl Display {
typst_utils::display(move |f| match color {
Color::Rgb(_) | Color::Cmyk(_) | Color::Luma(_) => rgb(f, color.to_rgb()),
Color::Oklab(v) => oklab(f, v),
Color::Oklch(v) => oklch(f, v),
Color::LinearRgb(v) => linear_rgb(f, v),
Color::Hsl(_) | Color::Hsv(_) => hsl(f, color.to_hsl()),
})
}
fn oklab(f: &mut fmt::Formatter<'_>, v: Oklab) -> fmt::Result {
write!(f, "oklab({} {} {}{})", percent(v.l), number(v.a), number(v.b), alpha(v.alpha))
}
fn oklch(f: &mut fmt::Formatter<'_>, v: Oklch) -> fmt::Result {
write!(
f,
"oklch({} {} {}deg{})",
percent(v.l),
number(v.chroma),
number(v.hue.into_degrees()),
alpha(v.alpha)
)
}
fn rgb(f: &mut fmt::Formatter<'_>, v: Rgb) -> fmt::Result {
if let Some(v) = rgb_to_8_bit_lossless(v) {
let (r, g, b, a) = v.into_components();
write!(f, "#{r:02x}{g:02x}{b:02x}")?;
if a != u8::MAX {
write!(f, "{a:02x}")?;
}
Ok(())
} else {
write!(
f,
"rgb({} {} {}{})",
percent(v.red),
percent(v.green),
percent(v.blue),
alpha(v.alpha)
)
}
}
/// Converts an f32 RGBA color to its 8-bit representation if the result is
/// [very close](is_very_close) to the original.
fn rgb_to_8_bit_lossless(
v: Rgb,
) -> Option<palette::rgb::Rgba<palette::encoding::Srgb, u8>> {
let l = v.into_format::<u8, u8>();
let h = l.into_format::<f32, f32>();
(is_very_close(v.red, h.red)
&& is_very_close(v.blue, h.blue)
&& is_very_close(v.green, h.green)
&& is_very_close(v.alpha, h.alpha))
.then_some(l)
}
fn linear_rgb(f: &mut fmt::Formatter<'_>, v: LinearRgb) -> fmt::Result {
write!(
f,
"color(srgb-linear {} {} {}{})",
percent(v.red),
percent(v.green),
percent(v.blue),
alpha(v.alpha),
)
}
fn hsl(f: &mut fmt::Formatter<'_>, v: Hsl) -> fmt::Result {
write!(
f,
"hsl({}deg {} {}{})",
number(v.hue.into_degrees()),
percent(v.saturation),
percent(v.lightness),
alpha(v.alpha),
)
}
/// Displays an alpha component if it not 1.
fn alpha(value: f32) -> impl Display {
typst_utils::display(move |f| {
if !is_very_close(value, 1.0) {
write!(f, " / {}", percent(value))?;
}
Ok(())
})
}
/// Displays a rounded percentage.
///
/// For a percentage, two significant digits after the comma gives us a
/// precision of 1/10_000, which is more than 12 bits (see `is_very_close`).
fn percent(ratio: f32) -> impl Display {
typst_utils::display(move |f| {
write!(f, "{}%", typst_utils::round_with_precision(ratio as f64 * 100.0, 2))
})
}
/// Rounds a number for display.
///
/// For a number between 0 and 1, four significant digits give us a
/// precision of 1/10_000, which is more than 12 bits (see `is_very_close`).
fn number(value: f32) -> impl Display {
typst_utils::round_with_precision(value as f64, 4)
}
/// Whether two component values are close enough that there is no
/// difference when encoding them with 12-bit. 12 bit is the highest
/// reasonable color bit depth found in the industry.
fn is_very_close(a: f32, b: f32) -> bool {
const MAX_BIT_DEPTH: u32 = 12;
const EPS: f32 = 0.5 / 2_i32.pow(MAX_BIT_DEPTH) as f32;
(a - b).abs() < EPS
}
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