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Functions to calculate luminance of colors and contrast ratio of colors in SASS
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| // Calulates power with integer exponent | |
| @function pow($number, $exponent) { | |
| $value: 1; | |
| @if $exponent > 0 { | |
| @for $i from 1 through $exponent { | |
| $value: $value * $number; | |
| } | |
| } @else if $exponent < 0 { | |
| @for $i from 1 through -$exponent { | |
| $value: $value / $number; | |
| } | |
| } | |
| @return $value; | |
| } | |
| // Calculates nth root with iteration | |
| @function nth-root($value, $n) { | |
| $precision: 1e-10; | |
| $previous: 0; | |
| $current: $value; | |
| @while abs($current - $previous) > $precision { | |
| $previous: $current; | |
| $current: 1 / $n * (($n - 1) * $previous + ($value / pow($previous, $n - 1))); | |
| } | |
| @return $current; | |
| } | |
| // Calculates luminance of a color based on the WCAG2 standard | |
| // Luminance calculation based on: https://www.w3.org/TR/WCAG20/#relativeluminancedef | |
| @function luminance($color) { | |
| $R: red($color) / 255; | |
| $G: green($color) / 255; | |
| $B: blue($color) / 255; | |
| @if $R <= 0.03928 { | |
| $R: $R / 12.92; | |
| } @else { | |
| $R: nth-root(pow($R + 0.055 / 1.055, 24), 10); | |
| } | |
| @if $G <= 0.03928 { | |
| $G: $G / 12.92; | |
| } @else { | |
| $G: nth-root(pow($G + 0.055 / 1.055, 24), 10); | |
| } | |
| @if $B <= 0.03928 { | |
| $B: $B / 12.92; | |
| } @else { | |
| $B: nth-root(pow($B + 0.055 / 1.055, 24), 10); | |
| } | |
| @return $R * 0.2126 + $G * 0.7152 + $B * 0.0722; | |
| } | |
| // Calculates the contrast of two colors based on the WCAG2 standard | |
| // Constrast calculation based on: https://www.w3.org/TR/WCAG20/#contrast-ratiodef | |
| @function contrast($color1, $color2) { | |
| @if luminance($color1) > luminance($color2) { | |
| @return (luminance($color1) + 0.05) / (luminance($color2) + 0.05); | |
| } @else { | |
| @return (luminance($color2) + 0.05) / (luminance($color1) + 0.05); | |
| } | |
| } |
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