ionic-framework/ionic/util/functions.scss

// Color Functions
// --------------------------------------------------

@function color-brightness($color-value) {
  @if (type-of($color-value) != color) {
    @return color-error($color-value);
  }

  @return (red($color-value) * .299 + green($color-value) * .587 + blue($color-value) * .114) / 255 * 100%;
}


@function color-inverse($color-value, $dark: #000, $light: #fff) {
  @if (type-of($color-value) != color) {
    @return color-error($color-value);
  }

  $brightness: color-brightness($color-value);
  $red: red($color-value);
  $green: green($color-value);

  @if ($brightness > 79) {
    @return $dark;
  }

  @if ($green > 240) {
    @return $dark;
  }

  @if ($red > 220 and $green > 180) {
    @return $dark;
  }

  @return $light;
}

// Pass dark and light colors based on the mode
// this is mostly used for toolbar buttons/titles
//
// @param {String} $color-value - color to get the inverse of
// @param {Boolean} $custom-contrast-mode - the mode to use
// in order to pass the custom colors
//
// @return {Color}
// --------------------------------------------------
@function mode-inverse($color-value, $custom-contrast-mode) {
  $dark: #000;
  $light: #fff;

  @if ($custom-contrast-mode == md) {
    $dark: #424242;
    $light: #fff;
  } @else if ($custom-contrast-mode == ios) {
    $dark: color($colors-ios, primary);
    $light: #fff;
  }

  @return color-inverse($color-value, $dark, $light);
}


@function color-shade($color-value, $amount:8%) {
  @if (type-of($color-value) != color) {
    @return color-error($color-value);
  }

  $lightness: lightness($color-value);

  $shade: #fff;

  @if ($lightness > 50) {
    $shade: #000;
  }

  @return mix($shade, $color-value, $amount);
}

@function color-error($color-value) {
  @error "

  The value `#{$color-value}` must be a color.
  If you are setting the value as a map make sure
  both the base and contrast are defined as colors.

  For example:

  $colors: (
    primary:    #327eff,
    secondary:  (base: #32db64, contrast: #000),
  );";

  @return false;
}

// Copy Colors Map
// --------------------------------------------------

@function copy-colors($colors-map) {
  @return map-merge($colors-map, ());
}


// String Replace Function
// --------------------------------------------------

@function str-replace($string, $search, $replace: "") {
  $index: str-index($string, $search);

  @if $index {
    @return str-slice($string, 1, $index - 1) + $replace + str-replace(str-slice($string, $index + str-length($search)), $search, $replace);
  }

  @return $string;
}


// URL Encode Function
// --------------------------------------------------

@function url-encode($val) {
  @return str-replace($val, " ", "%20");
}


// Fetch nested keys
// @param {Map} $map - Map
// @param {Arglist} $keys - Keys to fetch
// @return {*}
// --------------------------------------------------

@function map-fetch($map, $keys...) {
  @each $key in $keys {
    $map: map-get($map, $key);
  }

  @return $map;
}


// Fetch map color value
// @param {Map} $map - Map
// @param {String} $color-name - Color name to get
// @param {String} $color-key - Color key (optional), default base
// @return {Color}
// --------------------------------------------------

@function color($map, $color-name, $color-key:null) {
  // Get the value from $color-name in the map
  // this can be of type color or a map
  $color-value: map-get($map, $color-name);

  // If we were given a map we need to grab the value
  // of the key that is passed or the base key
  @if(type-of($color-value) == map) {
    @if($color-key) {
      $color-value: map-fetch($map, $color-name, $color-key);
    } @else {
      $color-value: map-fetch($map, $color-name, base);
    }
  }

  // If it isn't a map then return the value
  @return $color-value;
}

// Get the color map key based on the value
// if it doesn't exist then return the value
// --------------------------------------------------
@function color-key($colors, $value) {
  @each $color-name, $color-value in $colors {
    $base-value: color($colors, $color-name);
    @if ($base-value == $value) {
      @return map-get($colors, $color-name);
    }
  }

  @return $value;
}

// Fetch map color contrast
// @param {Map} $colors - colors map
// @param {String} $value - color value or color name
//
// Example values
// --------------------------------------------------
// primary | #327eff   | #444
// map key | map value | hex color not in map
// --------------------------------------------------
//
// @param {Boolean} $custom-contrast-mode - use custom
// contrast function
// @return {Color}
// --------------------------------------------------
@function color-contrast($colors, $value, $custom-contrast-mode: null) {
  $color-value: null;

  // If the value is a color (e.g. #fff)
  // we need to call color-key to see if
  // it exists in the color map or not
  @if (type-of($value) == color) {
    $color-value: color-key($colors, $value);

  // If the value is a string (e.g. primary)
  // we want to get the value from the map
  // where it is the key
  } @else {
    $color-value: map-get($colors, $value);
  }

  // If the value is a map then get the contrast
  // from the map (e.g. (base: #327eff, contrast: blue))
  @if (type-of($color-value) == map) {
    // If the map has the contrast key then use that
    // otherwise it is a map with just a base so get
    // the inverse of that base color
    @if map-has-key($color-value, contrast) {
      $color-value: map-get($color-value, contrast);
    } @else {
      $color-value: color-inverse(map-get($color-value, base));
    }

  // If a mode was passed we need to call
  // the custom inverse function to get the inverse
  // color based on the mode
} @elseif ($custom-contrast-mode) {
    $color-value: mode-inverse($color-value, $custom-contrast-mode);

  // Otherwise we were passed a color and can use the
  // function to get the inverse of that color
  // (e.g. #f4f4f4)
  } @else {
    $color-value: color-inverse($color-value);
  }

  // If the final value being returned is not a color
  // we should error
  @if (type-of($color-value) != color) {
    @return color-error($color-value);
  }

  @return $color-value;
}


// Create a list using the colors map
// @param {Map} $colors - colors map
// @return {List} $color-name, $color-base, $color-contrast
// ----------------------------------------------------------
@function get-colors($colors) {
  $colors-list: ();

  @each $color-name, $color-value in $colors {
    $color-base: null;
    $color-contrast: null;

    @if(type-of($color-value) == map) {
      $color-base: map-get($color-value, base);
      $color-contrast: map-get($color-value, contrast);
    } @else {
      $color-base: $color-value;
      $color-contrast: color-inverse($color-value);
    }

    $colors-list: append($colors-list, ($color-name, $color-base, $color-contrast), comma);
  }

  @return $colors-list;
}