README

This package is intended to provide a variety of SASS-like color manipulation functions.

Requirements

Composer, PHP 7.0 or later.

Installation

Install using Composer:

composer require ssnepenthe/color-utils

Usage

All functions listed are within the SSNepenthe\ColorUtils namespace.

Color Representation

Create Color objects using the color function:

color(array $color)

$color is an array of $channel => $value pairs. Valid channels are red, green, blue, hue, saturation, lightness and alpha.

• color(['red' => 255, 'green' => 0, 'blue' => 51])
• color(['hue' => 348, 'saturation' => 100, 'lightness' => 50, 'alpha' => 0.7])

color(string $color)

$color is a string representation of a color in one of the following formats:

• Hex notation: '#f03' or '#ff0033'
• Keyword notation: 'white' (list of valid keywords on MDN)
• Functional hsl(a) notation: 'hsl(348, 100%, 50%) or 'hsla(348, 100%, 50%, 0.7)'
• Functional rgb(a) notation: 'rgb(255, 0, 51)' or 'rgba(255, 0, 51, 0.7)'

color(int $red, int $green, int $blue, [float $alpha])

0 - 255 range for each of $red, $green and $blue, 0 - 1 for $alpha.

• color(255, 0, 51)
• color(255, 0, 51, 0.7)

color(float $hue, float $saturation, float $lightness, [float $alpha])

0 - 360 range for $hue, 0 - 100 for each of $saturation and $lightness, 0 - 1 for $alpha.

• color(348.0, 100.0, 50.0)
• color(348.0, 100.0, 50.0, 0.7)

Regarding the previous two examples:

The values 255, 0 and 51 could technically represent RGB values as well as HSL values. In cases like this, RGB takes precedence over HSL.

If you need finer control, use the following functions:

hsl(float $hue, float $saturation, float $lightness)

hsla(float $hue, float $saturation, float $lightness, float $alpha)

rgb(int $red, int $green, int $blue)

rgba(int $red, int $green, int $blue, float $alpha)

Lastly, the hsla and rgba functions can also be used to adjust the transparency of an existing color:

$hsl = hsl(348, 100, 50);
echo $hsl; // 'hsl(348, 100%, 50%)'

$hsla = hsla($hsl, 0.7);
echo $hsla; // 'hsla(348, 100%, 50%, 0.7)'

Color Components

Individual color components are accessible using the following functions (which each accept any $color argument recognized by the color function, including a complete color object):

alpha($color)

Get the alpha channel of a color.

• alpha('#f03'); // 1.0

blue($color)

Get the blue channel of a color.

• blue('#f03'); // 51

brightness($color)

Calculates color brightness on a scale from 0 (black) to 255 (white).

• brightness('#f03') // 82.059

green($color)

Get the green channel of a color.

• green('#f03'); // 0

hue($color)

Get the hue channel of a color.

• hue('#f03'); // 348.0

is_bright($color)

Accepts an optional $threshold float as the last parameter with a default of 127.5. Checks brightness($color) >= $threshold.

• is_bright('#f03'); // false
• is_bright('#f03', 82); // true

is_light($color)

Accepts an optional $threshold float as the last parameter with a default of 50.0. Checks lightness($color) >= $threshold.

• is_light('#f03'); // true
• is_light('#f03', 55); // false

lightness($color)

Get the lightness channel of a color.

• lightness('#f03'); // 50.0

looks_bright($color)

Accepts an optional $threshold float as the last parameter with a default of 127.5. Checks perceived_brightness($color) >= $threshold.

• looks_bright('#f03'); // true
• looks_bright('#f03', 141.0); // false

name($color)

Get the name (keyword) representation of a color. Returns an empty string if none is found.

• name('#f03'); // ''
• name('#00f'); // 'blue'

opacity($color)

Alias of alpha($color).

perceived_brightness($color)

Calculates the perceived brightness of a color on a scale from 0 (black) to 255 (white).

• perceived_brightness('#f03'); // 140.49551

red($color)

Get the red channel of a color.

• red('#f03'); // 255

relative_luminance($color)

Calculates the relative luminance of a color on a scale from 0 (black) to 1 (white).

• relative_luminance('#f03'); // 0.21499

saturation($color)

Get the saturation channel of a color.

• saturation('#f03'); // 100.0

Color Calculations

The following functions calculate differences between two given colors:

brightness_difference(Color $color1, Color $color2)

Calculates brightness difference on a scale from 0 to 255.

• brightness_difference(color('red'), color('green')) // 1.109

color_difference(Color $color1, Color $color2)

Calculates color difference on a scale from 0 to 765.

• color_difference(color('red'), color('green')) // 383

constrast_ratio(Color $color1, Color $color2)

Calculates the contrast ratio between two colors on a scale from 1 to 21.

• contrast_ratio(color('red'), color('green')) // 1.28486

Color Transformations

Colors can be transformed using the following functions (all accept any $color argument recognized by the color function):

adjust_color($color, array $channels)

Creates a new color by increasing/decreasing one or more channel values of $color. This can change red, green, blue, hue, saturation, lightness and alpha channels. $channels are specified as an array of $channel => $amount pairs.

• (string) adjust_color('rgb(50, 100, 150)', ['green' => 50, 'blue' => -50]); // 'rgb(50, 150, 100)'

change_color($color, array $channels)

Creates a new color by changing one or more channel values of $color. This can change red, green, blue, hue, saturation, lightness and alpha channels. $channels are specified as an array of $channel => $amount pairs.

• (string) change_color('rgb(50, 100, 150)', ['green' => 50, 'blue' => 25]); // 'rgb(50, 50, 25)'

invert($color)

Creates a new color by inverting (subtracting from 255) the red, green and blue channels of $color. Alpha is left unchanged.

• (string) invert('rgb(50, 100, 150)'); // 'rgb(205, 155, 105)'

mix(Color $color1, Color $color2, int $weight = 50)

Creates a new color by averaging the red, green and blue channels from $color1 and $color2, with $color1 optionally weighted by $weight%. Alpha is also considered. Uses the same algorithm as SASS.

• (string) mix(color('rgb(50, 100, 150)'), color('rgb(100, 100, 100)')); // 'rgb(75, 100, 125)
• (string) mix(color('rgb(50, 100, 150)'), color('rgb(100, 100, 100)'), 25); // 'rgb(88, 100, 113)
• (string) mix(color('rgb(50, 100, 150)'), color('rgb(100, 100, 100)'), 75); // 'rgb(63, 100, 138)

scale_color($color, array $channels)

Creates a new color by scaling one or more channel values of $color. This can change red, green, blue, hue, saturation, lightness and alpha channels. $channels are specified as an array of $channel => $percent pairs, and each channel value is scaled by $percent% of the max possible adjustment.

In the example below, green is 100 and we want to scale positively by 50%. The maximum allowed value is 255 which means the maximum possible adjustment is 155. The new green value then becomes 100 + (155 * 0.5).

Likewise, blue is 150 and we want to scale negatively by 50%. The minimum allowed value is 0 which means the maximum possible adjustment is -150. The new blue value then becomes 150 + (-150 * 0.5).

• (string) scale_color('rgb(50, 100, 150)', ['green' => 50, 'blue' => -50]); // 'rgb(50, 178, 75)'

adjust_hue($color, float $degrees)

Alias of adjust_color($color, ['hue' => $degrees]).

complement($color)

Alias of adjust_color($color, ['hue' => 180]).

darken($color, float $amount)

Alias of adjust_color($color, ['lightness' => -1 * $amount]).

desaturate($color, float $amount)

Alias of adjust_color($color, ['saturation' => -1 * $amount]).

fade_in($color, float $amount)

Alias of opacify($color, $amount).

fade_out($color, float $amount)

Alias of transparentize($color, $amount).

grayscale($color)

Alias of change_color($color, ['saturation' => 0]).

lighten($color, float $amount)

Alias of adjust_color($color, ['lightness' => $amount]).

opacify($color, float $amount)

Alias of adjust_color($color, ['alpha' => $amount]).

saturate($color, float $amount)

Alias of adjust_color($color, ['saturation' => $amount]).

shade($color, int $weight = 50)

Alias of mix(color('black'), color($color), $weight).

tint($color, int $weight = 50)

Alias of mix(color('white'), color($color), $weight).

transparentize($color, float $amount)

Alias of adjust_color($color, ['alpha' => -1 * $amount]).