pub trait RelativeContrast: Sized {
type Scalar: Real + PartialCmp;
// Required method
fn get_contrast_ratio(self, other: Self) -> Self::Scalar;
// Provided methods
fn has_min_contrast_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask { ... }
fn has_min_contrast_large_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask { ... }
fn has_enhanced_contrast_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask { ... }
fn has_enhanced_contrast_large_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask { ... }
fn has_min_contrast_graphics(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask { ... }
}palette::color_difference::Wcag21RelativeContrastExpand description
A trait for calculating relative contrast between two colors.
W3C’s Web Content Accessibility Guidelines (WCAG) 2.1 suggest a method to calculate accessible contrast ratios of text and background colors for those with low vision or color deficiencies, and for contrast of colors used in user interface graphics objects.
These criteria are recommendations, not hard and fast rules. Most importantly, look at the colors in action and make sure they’re clear and comfortable to read. A pair of colors may pass contrast guidelines but still be uncomfortable to look at. Favor readability over only satisfying the contrast ratio metric. It is recommended to verify the contrast ratio in the output format of the colors and not to assume the contrast ratio remains exactly the same across color formats. The following example checks the contrast ratio of two colors in RGB format.
use std::str::FromStr;
use palette::{Srgb, RelativeContrast};
// the rustdoc "DARK" theme background and text colors
let background: Srgb<f32> = Srgb::from(0x353535).into_format();
let foreground = Srgb::from_str("#ddd")?.into_format();
assert!(background.has_enhanced_contrast_text(foreground));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
color both in sRGB linear space. A higher contrast ratio is generally
desirable.
For more details, visit the following links:
Success Criterion 1.4.3 Contrast (Minimum) (Level AA)
Required Associated Types§
sourcetype Scalar: Real + PartialCmp
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
type Scalar: Real + PartialCmp
palette::color_difference::Wcag21RelativeContrastThe type of the contrast ratio.
Required Methods§
sourcefn get_contrast_ratio(self, other: Self) -> Self::Scalar
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn get_contrast_ratio(self, other: Self) -> Self::Scalar
palette::color_difference::Wcag21RelativeContrastCalculate the contrast ratio between two colors.
Provided Methods§
sourcefn has_min_contrast_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn has_min_contrast_text( self, other: Self, ) -> <Self::Scalar as HasBoolMask>::Mask
palette::color_difference::Wcag21RelativeContrastVerify the contrast between two colors satisfies SC 1.4.3. Contrast is at least 4.5:1 (Level AA).
sourcefn has_min_contrast_large_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn has_min_contrast_large_text( self, other: Self, ) -> <Self::Scalar as HasBoolMask>::Mask
palette::color_difference::Wcag21RelativeContrastVerify the contrast between two colors satisfies SC 1.4.3 for large text. Contrast is at least 3:1 (Level AA).
sourcefn has_enhanced_contrast_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn has_enhanced_contrast_text( self, other: Self, ) -> <Self::Scalar as HasBoolMask>::Mask
palette::color_difference::Wcag21RelativeContrastVerify the contrast between two colors satisfies SC 1.4.6. Contrast is at least 7:1 (Level AAA).
sourcefn has_enhanced_contrast_large_text(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn has_enhanced_contrast_large_text( self, other: Self, ) -> <Self::Scalar as HasBoolMask>::Mask
palette::color_difference::Wcag21RelativeContrastVerify the contrast between two colors satisfies SC 1.4.6 for large text. Contrast is at least 4.5:1 (Level AAA).
sourcefn has_min_contrast_graphics(
self,
other: Self,
) -> <Self::Scalar as HasBoolMask>::Mask
👎Deprecated since 0.7.2: replaced by palette::color_difference::Wcag21RelativeContrast
fn has_min_contrast_graphics( self, other: Self, ) -> <Self::Scalar as HasBoolMask>::Mask
palette::color_difference::Wcag21RelativeContrastVerify the contrast between two colors satisfies SC 1.4.11 for graphical objects. Contrast is at least 3:1 (Level AA).