Add traits for color schemes from traditional color theory

palette/src/color_theory.rs

@@ -0,0 +1,289 @@
+//! Traits related to traditional color theory.
+//!
+//! Traditional color theory is sometimes used as a guide when selecting colors
+//! for artistic purposes. While it's not the same as modern color science, and
+//! much more subjective, it may still be a helpful set of principles.
+//!
+//! This module is primarily based on the 12 color wheel, meaning that they use
+//! colors that are separated by 30° around the hue circle. There are however
+//! some concepts, such as [`Complementary`] colors, that are generally
+//! independent from the 12 color wheel concept.
+//!
+//! Most of the traits in this module require the color space to have a hue
+//! component. You will often see people use [`Hsv`][crate::Hsv] or
+//! [`Hsl`][crate::Hsl] when demonstrating some of these techniques, but Palette
+//! lets you use any hue based color space. Some traits are also implemented for
+//! other color spaces, when it's possible to avoid converting them to their hue
+//! based counterparts.
+
+use crate::{angle::HalfRotation, num::Real, ShiftHue};
+
+/// Represents the complementary color scheme.
+///
+/// A complementary color scheme consists of two colors on the opposite sides of
+/// the color wheel.
+pub trait Complementary: Sized {
+    /// Return the complementary color of `self`.
+    ///
+    /// This is the same as if the hue of `self` would be rotated by 180°.
+    ///
+    /// The following example makes a complementary color pair:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(300deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::Complementary};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 8.0, 0.5);
+    /// let complementary = primary.complementary();
+    ///
+    /// let hues = (
+    ///     primary.hue.into_positive_degrees(),
+    ///     complementary.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (120.0, 300.0));
+    /// ```
+    fn complementary(self) -> Self;
+}
+
+impl<T> Complementary for T
+where
+    T: ShiftHue,
+    T::Scalar: HalfRotation,
+{
+    fn complementary(self) -> Self {
+        self.shift_hue(T::Scalar::half_rotation())
+    }
+}
+
+/// Represents the split complementary color scheme.
+///
+/// A split complementary color scheme consists of three colors, where the
+/// second and third are adjacent to (30° away from) the complementary color of
+/// the first.
+pub trait SplitComplementary: Sized {
+    /// Return the two split complementary colors of `self`.
+    ///
+    /// The colors are ordered by ascending hue, or `(hue+150°, hue+210°)`.
+    /// Combined with the input color, these make up 3 adjacent colors.
+    ///
+    /// The following example makes a split complementary color scheme:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(270deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(330deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::SplitComplementary};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 8.0, 0.5);
+    /// let (complementary1, complementary2) = primary.split_complementary();
+    ///
+    /// let hues = (
+    ///     primary.hue.into_positive_degrees(),
+    ///     complementary1.hue.into_positive_degrees(),
+    ///     complementary2.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (120.0, 270.0, 330.0));
+    /// ```
+    fn split_complementary(self) -> (Self, Self);
+}
+
+impl<T> SplitComplementary for T
+where
+    T: ShiftHue + Clone,
+    T::Scalar: Real,
+{
+    fn split_complementary(self) -> (Self, Self) {
+        let first = self.clone().shift_hue(T::Scalar::from_f64(150.0));
+        let second = self.shift_hue(T::Scalar::from_f64(210.0));
+
+        (first, second)
+    }
+}
+
+/// Represents the analogous color scheme on a 12 color wheel.
+///
+/// An analogous color scheme consists of three colors next to each other (30°
+/// apart) on the color wheel.
+pub trait Analogous: Sized {
+    /// Return the two additional colors of an analogous color scheme.
+    ///
+    /// The colors are ordered by ascending hue difference, or `(hue-30°,
+    /// hue+30°)`. Combined with the input color, these make up 3 adjacent
+    /// colors.
+    ///
+    /// The following example makes a 3 color analogous scheme:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(90deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(150deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::Analogous};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 0.8, 0.5);
+    /// let (analog_down, analog_up) = primary.analogous();
+    ///
+    /// let hues = (
+    ///     analog_down.hue.into_positive_degrees(),
+    ///     primary.hue.into_positive_degrees(),
+    ///     analog_up.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (90.0, 120.0, 150.0));
+    /// ```
+    fn analogous(self) -> (Self, Self);
+
+    /// Return the two furthest colors of a 5 color analogous color scheme.
+    ///
+    /// The colors are ordered by ascending hue difference, or `(hue-60°,
+    /// hue+60°)`. Combined with the input color and the colors from
+    /// `analogous`, these make up 5 adjacent colors.
+    ///
+    /// The following example makes a 5 color analogous scheme:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(60deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(90deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(150deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(180deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::Analogous};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 0.8, 0.5);
+    /// let (analog_down1, analog_up1) = primary.analogous();
+    /// let (analog_down2, analog_up2) = primary.analogous2();
+    ///
+    /// let hues = (
+    ///     analog_down2.hue.into_positive_degrees(),
+    ///     analog_down1.hue.into_positive_degrees(),
+    ///     primary.hue.into_positive_degrees(),
+    ///     analog_up1.hue.into_positive_degrees(),
+    ///     analog_up2.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (60.0, 90.0, 120.0, 150.0, 180.0));
+    /// ```
+    fn analogous2(self) -> (Self, Self);
+}
+
+impl<T> Analogous for T
+where
+    T: ShiftHue + Clone,
+    T::Scalar: Real,
+{
+    fn analogous(self) -> (Self, Self) {
+        let first = self.clone().shift_hue(T::Scalar::from_f64(330.0));
+        let second = self.shift_hue(T::Scalar::from_f64(30.0));
+
+        (first, second)
+    }
+
+    fn analogous2(self) -> (Self, Self) {
+        let first = self.clone().shift_hue(T::Scalar::from_f64(300.0));
+        let second = self.shift_hue(T::Scalar::from_f64(60.0));
+
+        (first, second)
+    }
+}
+
+/// Represents the triadic color scheme.
+///
+/// A triadic color scheme consists of thee colors at a 120° distance from each
+/// other.
+pub trait Triadic: Sized {
+    /// Return the two additional colors of a triadic color scheme.
+    ///
+    /// The colors are ordered by ascending relative hues, or `(hue+120°,
+    /// hue+240°)`.
+    ///
+    /// The following example makes a triadic scheme:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(240deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(0deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::Triadic};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 0.8, 0.5);
+    /// let (triadic1, triadic2) = primary.triadic();
+    ///
+    /// let hues = (
+    ///     primary.hue.into_positive_degrees(),
+    ///     triadic1.hue.into_positive_degrees(),
+    ///     triadic2.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (120.0, 240.0, 0.0));
+    /// ```
+    fn triadic(self) -> (Self, Self);
+}
+
+impl<T> Triadic for T
+where
+    T: ShiftHue + Clone,
+    T::Scalar: Real,
+{
+    fn triadic(self) -> (Self, Self) {
+        let first = self.clone().shift_hue(T::Scalar::from_f64(120.0));
+        let second = self.shift_hue(T::Scalar::from_f64(240.0));
+
+        (first, second)
+    }
+}
+
+/// Represents the tetradic, or square, color scheme.
+///
+/// A tetradic color scheme consists of four colors at a 90° distance from each
+/// other. These form two pairs of complementary colors.
+#[doc(alias = "Square")]
+pub trait Tetradic: Sized {
+    /// Return the three additional colors of a tetradic color scheme.
+    ///
+    /// The colors are ordered by ascending relative hues, or `(hue+90°,
+    /// hue+180°, hue+270°)`.
+    ///
+    /// The following example makes a tetradic scheme:
+    ///
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(120deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(210deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(300deg, 80%, 50%);"></div>
+    /// <div style="display: inline-block; width: 3em; height: 1em; border: 1px solid black; background: hsl(30deg, 80%, 50%);"></div>
+    ///
+    /// ```
+    /// use palette::{Hsl, color_theory::Tetradic};
+    ///
+    /// let primary = Hsl::new_srgb(120.0f32, 0.8, 0.5);
+    /// let (tetradic1, tetradic2, tetradic3) = primary.tetradic();
+    ///
+    /// let hues = (
+    ///     primary.hue.into_positive_degrees(),
+    ///     tetradic1.hue.into_positive_degrees(),
+    ///     tetradic2.hue.into_positive_degrees(),
+    ///     tetradic3.hue.into_positive_degrees(),
+    /// );
+    ///
+    /// assert_eq!(hues, (120.0, 210.0, 300.0, 30.0));
+    /// ```
+    fn tetradic(self) -> (Self, Self, Self);
+}
+
+impl<T> Tetradic for T
+where
+    T: ShiftHue + Clone,
+    T::Scalar: Real,
+{
+    fn tetradic(self) -> (Self, Self, Self) {
+        let first = self.clone().shift_hue(T::Scalar::from_f64(90.0));
+        let second = self.clone().shift_hue(T::Scalar::from_f64(180.0));
+        let third = self.shift_hue(T::Scalar::from_f64(270.0));
+
+        (first, second, third)
+    }
+}

palette/src/lab.rs

@@ -231,6 +231,7 @@ impl_lighten!(Lab<Wp> increase {l => [Self::min_l(), Self::max_l()]} other {a, b
 impl_premultiply!(Lab<Wp> {l, a, b} phantom: white_point);
 impl_euclidean_distance!(Lab<Wp> {l, a, b});
 impl_hyab!(Lab<Wp> {lightness: l, chroma1: a, chroma2: b});
+impl_lab_color_schemes!(Lab<Wp>[l, white_point]);
 
 impl<Wp, T> GetHue for Lab<Wp, T>
 where
@@ -389,6 +390,9 @@ mod test {
     use super::Lab;
     use crate::white_point::D65;
 
+    #[cfg(feature = "approx")]
+    use crate::Lch;
+
     test_convert_into_from_xyz!(Lab);
 
     #[cfg(feature = "approx")]
@@ -476,4 +480,6 @@ mod test {
         min: Lab::new(0.0f32, -128.0, -128.0),
         max: Lab::new(100.0, 127.0, 127.0)
     }
+
+    test_lab_color_schemes!(Lab/Lch [l, white_point]);
 }

palette/src/lib.rs

@@ -347,6 +347,7 @@ pub mod bool_mask;
 pub mod cast;
 pub mod chromatic_adaptation;
 pub mod color_difference;
+pub mod color_theory;
 pub mod convert;
 pub mod encoding;
 pub mod hsl;

palette/src/luv.rs

@@ -233,6 +233,7 @@ impl_lighten!(Luv<Wp> increase {l => [Self::min_l(), Self::max_l()]} other {u, v
 impl_premultiply!(Luv<Wp> {l, u, v} phantom: white_point);
 impl_euclidean_distance!(Luv<Wp> {l, u, v});
 impl_hyab!(Luv<Wp> {lightness: l, chroma1: u, chroma2: v});
+impl_lab_color_schemes!(Luv<Wp>[u, v][l, white_point]);
 
 impl<Wp, T> GetHue for Luv<Wp, T>
 where
@@ -314,6 +315,9 @@ mod test {
     use super::Luv;
     use crate::white_point::D65;
 
+    #[cfg(feature = "approx")]
+    use crate::Lchuv;
+
     test_convert_into_from_xyz!(Luv);
 
     #[cfg(feature = "approx")]
@@ -417,4 +421,6 @@ mod test {
         min: Luv::new(0.0f32, -84.0, -135.0),
         max: Luv::new(100.0, 176.0, 108.0)
     }
+
+    test_lab_color_schemes!(Luv / Lchuv [u, v][l, white_point]);
 }

palette/src/macros.rs

@@ -37,3 +37,5 @@ mod copy_clone;
 mod hue;
 #[macro_use]
 mod random;
+#[macro_use]
+mod color_theory;