_functions.scss

@function minus1px($value) {
    $unit: unit($value);
    @if ($unit == px) {
      @return $value - 1;
    } @elseif ($unit == em or $unit == rem) {
      @return $value - (1 / 16);
    }
    @else {
      @error 'Unit `#{$unit}` not supported.';
  }
}


/*
    Colour contrast from https://gist.github.com/FStop/8959422
    
    Usage:
    @if color_contrast($colour, #fff) < 2 {
        color: #333;
    }
    @else{
        color: #fff;
    }
*/
/* Awesome contrast ratio function
* via https://gist.github.com/voxpelli/6304812
**/
@function color_luminance($color) {
  // Adapted from: https://github.com/LeaVerou/contrast-ratio/blob/gh-pages/color.js
  // Formula: http://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
  $rgba: red($color), green($color), blue($color);
  $rgba2: ();
 
  @for $i from 1 through 3 {
    $rgb: nth($rgba, $i);
    $rgb: $rgb / 255;
 
    $rgb: if($rgb < .03928, $rgb / 12.92, pow(($rgb + .055) / 1.055, 2.4));
 
    $rgba2: append($rgba2, $rgb);
  }
 
  @return .2126 * nth($rgba2, 1) + .7152 * nth($rgba2, 2) + 0.0722 * nth($rgba2, 3);
}

@function color_contrast($color1, $color2) {
  // Adapted from: https://github.com/LeaVerou/contrast-ratio/blob/gh-pages/color.js
  // Formula: http://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
  $luminance1: color_luminance($color1) + .05;
  $luminance2: color_luminance($color2) + .05;
  $ratio: $luminance1 / $luminance2;
 
  @if $luminance2 > $luminance1 {
    $ratio: 1 / $ratio;
  }
 
  $ratio: round($ratio * 10) / 10;
 
  @return $ratio;
}