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Implement alpha modification methods for colors (#3516)

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Co-authored-by: Laurenz <laurmaedje@gmail.com>
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frozolotl 2024-02-28 15:09:13 +01:00 committed by GitHub
parent a518e2dd4d
commit 9d8df00ffb
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2 changed files with 83 additions and 1 deletions
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68
crates/typst/src/visualize/color.rs
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@ -6,7 +6,7 @@ use ecow::{eco_format, EcoString, EcoVec};
use once_cell::sync::Lazy;
use palette::encoding::{self, Linear};
use palette::{
Darken, Desaturate, FromColor, Lighten, OklabHue, RgbHue, Saturate, ShiftHue,
Alpha, Darken, Desaturate, FromColor, Lighten, OklabHue, RgbHue, Saturate, ShiftHue,
};
use qcms::Profile;
@ -1128,6 +1128,47 @@ impl Color {
) -> StrResult<Color> {
Self::mix_iter(colors, space)
}
/// Makes a color more transparent by a given factor.
///
/// This method is relative to the existing alpha value.
/// If the scale is positive, calculates `alpha - alpha * scale`.
/// Negative scales behave like `color.opacify(-scale)`.
///
/// ```example
/// #block(fill: red)[opaque]
/// #block(fill: red.transparentize(50%))[half red]
/// #block(fill: red.transparentize(75%))[quarter red]
/// ```
#[func]
pub fn transparentize(
self,
/// The factor to change the alpha value by.
scale: Ratio,
) -> StrResult<Color> {
self.scale_alpha(-scale)
}
/// Makes a color more opaque by a given scale.
///
/// This method is relative to the existing alpha value.
/// If the scale is positive, calculates `alpha + scale - alpha * scale`.
/// Negative scales behave like `color.transparentize(-scale)`.
///
/// ```example
/// #let half-red = red.transparentize(50%)
/// #block(fill: half-red.opacify(100%))[opaque]
/// #block(fill: half-red.opacify(50%))[three quarters red]
/// #block(fill: half-red.opacify(-50%))[one quarter red]
/// ```
#[func]
pub fn opacify(
self,
/// The scale to change the alpha value by.
scale: Ratio,
) -> StrResult<Color> {
self.scale_alpha(scale)
}
}
impl Color {
@ -1265,6 +1306,31 @@ impl Color {
self
}
/// Scales the alpha value of a color by a given amount.
///
/// For positive scales, computes `alpha + scale - alpha * scale`.
/// For non-positive scales, computes `alpha + alpha * scale`.
fn scale_alpha(self, scale: Ratio) -> StrResult<Color> {
#[inline]
fn transform<C>(mut color: Alpha<C, f32>, scale: Ratio) -> Alpha<C, f32> {
let scale = scale.get() as f32;
let factor = if scale > 0.0 { 1.0 - color.alpha } else { color.alpha };
color.alpha = (color.alpha + scale * factor).clamp(0.0, 1.0);
color
}
Ok(match self {
Color::Luma(c) => Color::Luma(transform(c, scale)),
Color::Oklab(c) => Color::Oklab(transform(c, scale)),
Color::Oklch(c) => Color::Oklch(transform(c, scale)),
Color::Rgb(c) => Color::Rgb(transform(c, scale)),
Color::LinearRgb(c) => Color::LinearRgb(transform(c, scale)),
Color::Cmyk(_) => bail!("CMYK does not have an alpha component"),
Color::Hsl(c) => Color::Hsl(transform(c, scale)),
Color::Hsv(c) => Color::Hsv(transform(c, scale)),
})
}
/// Converts the color to a vec of four floats.
pub fn to_vec4(&self) -> [f32; 4] {
match self {

16
tests/typ/compiler/color.typ
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@ -83,3 +83,19 @@
#test-repr(luma(20%).lighten(50%), luma(60%))
#test-repr(luma(80%).darken(20%), luma(64%))
#test-repr(luma(80%).negate(space: luma), luma(20%))
---
// Test alpha modification.
// Ref: false
#test-repr(luma(100%, 100%).transparentize(50%), luma(100%, 50%))
#test-repr(luma(100%, 100%).transparentize(75%), luma(100%, 25%))
#test-repr(luma(100%, 50%).transparentize(50%), luma(100%, 25%))
#test-repr(luma(100%, 10%).transparentize(250%), luma(100%, 0%))
#test-repr(luma(100%, 40%).transparentize(-50%), luma(100%, 70%))
#test-repr(luma(100%, 0%).transparentize(-100%), luma(100%, 100%))
#test-repr(luma(100%, 50%).opacify(50%), luma(100%, 75%))
#test-repr(luma(100%, 20%).opacify(100%), luma(100%, 100%))
#test-repr(luma(100%, 100%).opacify(250%), luma(100%, 100%))
#test-repr(luma(100%, 50%).opacify(-50%), luma(100%, 25%))
#test-repr(luma(100%, 0%).opacify(0%), luma(100%, 0%))