Move contrast ratio calculation to standalone fn

Refactor implementations to use standalone function

palette/src/hsl.rs

@@ -8,7 +8,7 @@ use core::ops::{Add, AddAssign, Sub, SubAssign};
 use encoding::pixel::RawPixel;
 use encoding::{Linear, Srgb};
 use rgb::{Rgb, RgbSpace};
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {Alpha, Hsv, RgbHue, Xyz};
 use {
     Component, FloatComponent, FromColor, FromF64, GetHue, Hue, IntoColor, Limited, Mix, Pixel,
@@ -631,15 +631,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/hsv.rs

@@ -8,7 +8,7 @@ use core::ops::{Add, AddAssign, Sub, SubAssign};
 use encoding::pixel::RawPixel;
 use encoding::{Linear, Srgb};
 use rgb::{Rgb, RgbSpace};
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {Alpha, Hsl, Hwb, RgbHue, Xyz};
 use {
     Component, FloatComponent, FromColor, FromF64, GetHue, Hue, IntoColor, Limited, Mix, Pixel,
@@ -644,15 +644,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/hwb.rs

@@ -8,7 +8,7 @@ use core::ops::{Add, AddAssign, Sub, SubAssign};
 use encoding::pixel::RawPixel;
 use encoding::Srgb;
 use rgb::RgbSpace;
-use {clamp, from_f64};
+use {clamp, contrast_ratio};
 use {Alpha, Hsv, RgbHue, Xyz};
 use {
     Component, FloatComponent, FromColor, FromF64, GetHue, Hue, IntoColor, Limited, Mix, Pixel,
@@ -592,15 +592,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/lab.rs

@@ -3,7 +3,7 @@ use core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 
 use encoding::pixel::RawPixel;
 use white_point::{WhitePoint, D65};
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {Alpha, LabHue, Lch, Xyz};
 use {
     Component, ComponentWise, FloatComponent, GetHue, IntoColor, Limited, Mix, Pixel,
@@ -634,15 +634,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/lch.rs

@@ -5,7 +5,7 @@ use color_difference::ColorDifference;
 use color_difference::{get_ciede_difference, LabColorDiff};
 use encoding::pixel::RawPixel;
 use white_point::{WhitePoint, D65};
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {Alpha, Lab, LabHue, Xyz};
 use {
     Component, FloatComponent, FromColor, GetHue, Hue, IntoColor, Limited, Mix, Pixel,
@@ -525,15 +525,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/lib.rs

@@ -189,7 +189,7 @@ pub use convert::{ConvertFrom, ConvertInto, FromColor, IntoColor, OutOfBounds};
 pub use encoding::pixel::Pixel;
 pub use hues::{LabHue, RgbHue};
 pub use matrix::Mat3;
-pub use relative_contrast::RelativeContrast;
+pub use relative_contrast::{contrast_ratio, RelativeContrast};
 
 //Helper macro for checking ranges and clamping.
 #[cfg(test)]

palette/src/luma/luma.rs

@@ -10,7 +10,7 @@ use encoding::pixel::RawPixel;
 use encoding::{Linear, Srgb, TransferFn};
 use luma::LumaStandard;
 use white_point::WhitePoint;
-use {clamp, from_f64};
+use {clamp, contrast_ratio};
 use {Alpha, Xyz, Yxy};
 use {
     Blend, Component, ComponentWise, FloatComponent, FromColor, FromComponent, IntoColor, Limited,
@@ -733,11 +733,10 @@ where
     type Scalar = T;
 
     fn get_contrast_ratio(&self, other: &Self) -> T {
-        if self.luma > other.luma {
-            (self.into_linear().luma + from_f64(0.05)) / (other.into_linear().luma + from_f64(0.05))
-        } else {
-            (other.into_linear().luma + from_f64(0.05)) / (self.into_linear().luma + from_f64(0.05))
-        }
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
+
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/relative_contrast.rs

@@ -1,3 +1,5 @@
+use component::Component;
+use core::ops::{Add, Div};
 use {from_f64, FromF64};
 
 /// A trait for calculating relative contrast between two colors.
@@ -32,10 +34,10 @@ use {from_f64, FromF64};
 /// }
 /// ```
 ///
-/// The possible range of ratios is from 1:1 to 21:1. There is a Success
-/// Criterion for Contrast (Minimum) and a Success Criterion for Contrast
-/// (Enhanced), SC 1.4.3 and SC 1.4.6 respectively, which are concerned with
-/// text and images of text. SC 1.4.11 is a Success Criterion for "non-text
+/// The possible range of contrast ratios is from 1:1 to 21:1. There is a
+/// Success Criterion for Contrast (Minimum) and a Success Criterion for
+/// Contrast (Enhanced), SC 1.4.3 and SC 1.4.6 respectively, which are concerned
+/// with text and images of text. SC 1.4.11 is a Success Criterion for "non-text
 /// contrast" such as user interface components and other graphics. The relative
 /// contrast is calculated by `(L1 + 0.05) / (L2 + 0.05)`, where `L1` is the
 /// luminance of the brighter color and `L2` is the luminance of the darker
@@ -49,6 +51,7 @@ use {from_f64, FromF64};
 /// [Success Criterion 1.4.6 Contrast (Enhanced) (Level AAA)](https://www.w3.org/WAI/WCAG21/Understanding/contrast-enhanced)
 ///
 /// [Success Criterion 1.4.11 Non-text Contrast (Level AA)](https://www.w3.org/WAI/WCAG21/Understanding/non-text-contrast.html)
+
 pub trait RelativeContrast {
     /// The type of the contrast ratio.
     type Scalar: FromF64 + PartialOrd;
@@ -82,6 +85,21 @@ pub trait RelativeContrast {
     }
 }
 
+/// Calculates a ratio between two `luma` values.
+pub fn contrast_ratio<T>(luma1: T, luma2: T) -> T
+where
+    T: Add<Output = T>,
+    T: Div<Output = T>,
+    T: FromF64,
+    T: Component,
+{
+    if luma1 > luma2 {
+        (luma1 + from_f64(0.05)) / (luma2 + from_f64(0.05))
+    } else {
+        (luma2 + from_f64(0.05)) / (luma1 + from_f64(0.05))
+    }
+}
+
 #[cfg(test)]
 mod test {
     use core::str::FromStr;

palette/src/rgb/rgb.rs

@@ -17,7 +17,7 @@ use luma::LumaStandard;
 use matrix::{matrix_inverse, multiply_xyz_to_rgb, rgb_to_xyz_matrix};
 use rgb::{RgbSpace, RgbStandard, TransferFn};
 use white_point::WhitePoint;
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {
     Blend, Component, ComponentWise, FloatComponent, FromComponent, GetHue, Limited, Mix, Pixel,
     RelativeContrast, Shade,
@@ -1048,15 +1048,11 @@ where
 {
     type Scalar = T;
 
-    fn get_contrast_ratio(&self, color: &Self) -> T {
-        let this = self.into_luma();
-        let other = color.into_luma();
+    fn get_contrast_ratio(&self, other: &Self) -> T {
+        let luma1 = self.into_luma();
+        let luma2 = other.into_luma();
 
-        if this.luma > other.luma {
-            (this.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (this.luma + from_f64(0.05))
-        }
+        contrast_ratio(luma1.luma, luma2.luma)
     }
 }
 

palette/src/xyz.rs

@@ -6,7 +6,7 @@ use luma::LumaStandard;
 use matrix::{multiply_rgb_to_xyz, rgb_to_xyz_matrix};
 use rgb::{Rgb, RgbSpace, RgbStandard};
 use white_point::{WhitePoint, D65};
-use {clamp, from_f64};
+use {clamp, contrast_ratio, from_f64};
 use {Alpha, Lab, Luma, Yxy};
 use {Component, ComponentWise, FloatComponent, Limited, Mix, Pixel, RelativeContrast, Shade};
 
@@ -608,11 +608,7 @@ where
     type Scalar = T;
 
     fn get_contrast_ratio(&self, other: &Self) -> T {
-        if self.y > other.y {
-            (self.y + from_f64(0.05)) / (other.y + from_f64(0.05))
-        } else {
-            (other.y + from_f64(0.05)) / (self.y + from_f64(0.05))
-        }
+        contrast_ratio(self.y, other.y)
     }
 }
 

palette/src/yxy.rs

@@ -4,7 +4,7 @@ use core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 use encoding::pixel::RawPixel;
 use luma::LumaStandard;
 use white_point::{WhitePoint, D65};
-use {clamp, from_f64};
+use {clamp, contrast_ratio};
 use {Alpha, Luma, Xyz};
 use {
     Component, ComponentWise, FloatComponent, IntoColor, Limited, Mix, Pixel, RelativeContrast,
@@ -577,11 +577,7 @@ where
     type Scalar = T;
 
     fn get_contrast_ratio(&self, other: &Self) -> T {
-        if self.luma > other.luma {
-            (self.luma + from_f64(0.05)) / (other.luma + from_f64(0.05))
-        } else {
-            (other.luma + from_f64(0.05)) / (self.luma + from_f64(0.05))
-        }
+        contrast_ratio(self.luma, other.luma)
     }
 }