As an extension to CSS, LESS is not only backwards compatible with CSS, but the extra features it adds use existing CSS syntax. This makes learning LESS a breeze, and if in doubt, lets you fall back to CSS.

Variables

These are pretty self-explanatory:

@nice-blue: #5B83AD;
@light-blue: (@nice-blue + #111);

#header { color: @light-blue; }

Outputs:

#header { color: #6c94be; }

It is also possible to define variables with a variable name:

@fnord: "I am fnord.";
@var: 'fnord';
content: @@var;

Which compiles to:

content: "I am fnord.";

When defining a variable twice, the last definition of the variable is used, searching from the current scope upwards. This is similar to css itself where the last property inside a definition is used to determine the value.

For instance:

@var: 0;
.class1 {
  @var: 1;
  .class {
    @var: 2;
    three: @var;
    @var: 3;
  }
  one: @var;
}

Compiles to:

.class1 .class {
  three: 3;
}
.class1 {
  one: 1;
}

Variables are lazy loaded and do not have to be declared before being used.

Valid less snippet:

lazy-eval {
  width: @var;
}

@var: @a;
@a: 9%;

this is valid less too:

.lazy-eval-scope {
  width: @var;
  @a: 9%;
}

@var: @a;
@a: 100%;

both compile into:

.lazy-eval-scope {
  width: 9%;
}

Mixins

In LESS, it is possible to include a bunch of properties from one ruleset into another ruleset. So say we have the following class:

.bordered {
  border-top: dotted 1px black;
  border-bottom: solid 2px black;
}

And we want to use these properties inside other rulesets. Well, we just have to drop in the name of the class in any ruleset we want to include its properties, like so:

#menu a {
  color: #111;
  .bordered;
}
.post a {
  color: red;
  .bordered;
}

The properties of the .bordered class will now appear in both #menu a and .post a:

#menu a {
  color: #111;
  border-top: dotted 1px black;
  border-bottom: solid 2px black;
}
.post a {
  color: red;
  border-top: dotted 1px black;
  border-bottom: solid 2px black;
}

Any CSS class or id ruleset can be mixed-in that way.

Note: Variables are also mixed in, so variables from a mixin will be placed into the current scope. This is contentious and may change in the future.

Parametric Mixins

LESS has a special type of ruleset which can be mixed in like classes, but accepts parameters. Here’s the canonical example:

.border-radius (@radius) {
  -moz-border-radius: @radius;
  -webkit-border-radius: @radius;
  border-radius: @radius;
}

And here’s how we can mix it into various rulesets:

#header {
  .border-radius(4px);
}
.button {
  .border-radius(6px);
}

Parametric mixins can also have default values for their parameters:

.border-radius (@radius: 5px) {
  -moz-border-radius: @radius;
  -webkit-border-radius: @radius;
  border-radius: @radius;
}

We can invoke it like this now:

#header {
  .border-radius;
}

And it will include a 5px border-radius.

You can also use parametric mixins which don’t take parameters. This is useful if you want to hide the ruleset from the CSS output, but want to include its properties in other rulesets:

.wrap () {
  text-wrap: wrap;
  white-space: -moz-pre-wrap;
  white-space: pre-wrap;
  word-wrap: break-word;
}

pre { .wrap }

Which would output:

pre {
  text-wrap: wrap;
  white-space: -moz-pre-wrap;
  white-space: pre-wrap;
  word-wrap: break-word;
}

Mixins With Multiple Parameters

Parameters are either semicolon or comma separated. It is recommended to use semicolon. The symbol comma has double meaning: it can be interpreted either as a mixin parameters separator or as css list separator. Using comma as mixin separator makes it impossible to use comma separated list as an argument.

Semicolon does not have such limitation. If the compiler sees at least one semicolon inside mixin call or declaration, it assumes that arguments are separated by semicolons. All commas then belong to css lists. For example:

• two arguments and each contains comma separated list: .name(1, 2, 3; something, else),
• three arguments and each contains one number: .name(1, 2, 3),
• use dummy semicolon to create mixin call with one argument containing comma separated css list: .name(1, 2, 3;),
• comma separated default value: .name(@param1: red, blue;).

It is legal to define multiple mixins with the same name and number of parameters. Less will use properties of all that can apply. For example, if you used the mixin with one parameter e.g. .mixin(green);, then properties of all mixins with exactly one mandatory parameter will be used:

.mixin(@color) {
  color-1: @color;
}
.mixin(@color; @padding:2) {
  color-2: @color;
  padding-2: @padding;
}
.mixin(@color; @padding; @margin: 2) {
  color-3: @color;
  padding-3: @padding;
  margin: @margin @margin @margin @margin;
}
.some .selector div {
  .mixin(#008000);
}

compiles into:

.some .selector div {
  color-1: #008000;
  color-2: #008000;
  padding-2: 2;
}

The @arguments variable

@arguments has a special meaning inside mixins, it contains all the arguments passed, when the mixin was called. This is useful if you don’t want to deal with individual parameters:

.box-shadow (@x: 0; @y: 0; @blur: 1px; @color: #000) {
  -moz-box-shadow: @arguments;
  -webkit-box-shadow: @arguments;
  box-shadow: @arguments;
}
.box-shadow(2px; 5px);

Which results in:

  -moz-box-shadow: 2px 5px 1px #000;
  -webkit-box-shadow: 2px 5px 1px #000;
  box-shadow: 2px 5px 1px #000;

Advanced arguments and the @rest variable

You can use ... if you want your mixin to take a variable number of arguments. Using this after a variable name will assign those arguments to the variable.

.mixin (...) {        // matches 0-N arguments
.mixin () {           // matches exactly 0 arguments
.mixin (@a: 1) {      // matches 0-1 arguments
.mixin (@a: 1; ...) { // matches 0-N arguments
.mixin (@a; ...) {    // matches 1-N arguments

Furthermore:

.mixin (@a; @rest...) {
   // @rest is bound to arguments after @a
   // @arguments is bound to all arguments
}

Return Values

Variables defined inside mixins act as return values and are usable in caller. Returned variables never rewrite callers local variables. Only variables not present in callers local scope are copied.

Variable defined in mixin acts as return value:

.mixin() { 
  @global: in-mixin;
  @local: in-mixin; 
  @definedOnlyInMixin: in-mixin; 
}

.class {
  @local: localy-defined-value; //local variable - protected
  margin: @global @local @definedOnlyInMixin;
  .mixin(); 
}

@global: outer-scope; // non-local variable - rewritten

Compiles into:

.class {
  margin: in-mixin localy-defined-value in-mixin;
}

Unlocking Mixins

Mixins defined in mixin are also usable in caller. There is no scope protection, mixins are unlocked even if the local scope contains mixin with the same name.

.unlock(@value) { // outer mixin
  .doSomething() { // nested mixin
    declaration: @value;
  }
}

.selector {
  .unlock(5); // unlock doSomething mixin - must be first
  .doSomething(); //nested mixin was copied here and is usable 
}

Compiles into:

.selector {
  declaration: 5;
}

Unlocked mixins are available only after they have been unlocked. Following would throw syntax error:

.doSomething(); // syntax error: nested mixin is not available yet
.unlock(5); // too late

The Keyword !important

Use the !important keyword after mixin call to mark all properties brought by it as !important:

Sample input:

.mixin (@a: 0) {
  border: @a;
  boxer: @a;
}
.unimportant {
  .mixin(1); 
}
.important {
  .mixin(2) !important; 
}

compiled into:

.unimportant {
  border: 1;
  boxer: 1;
}
.important {
  border: 2 !important;
  boxer: 2 !important;
}

Pattern-matching and Guard expressions

Sometimes, you may want to change the behaviour of a mixin, based on the parameters you pass to it. Let’s start with something basic:

.mixin (@s; @color) { ... }

.class {
  .mixin(@switch; #888);
}

Now let’s say we want .mixin to behave differently, based on the value of @switch, we could define .mixin as such:

.mixin (dark; @color) {
  color: darken(@color, 10%);
}
.mixin (light; @color) {
  color: lighten(@color, 10%);
}
.mixin (@_; @color) {
  display: block;
}

Now, if we run:

@switch: light;

.class {
  .mixin(@switch; #888);
}

We will get the following CSS:

.class {
  color: #a2a2a2;
  display: block;
}

Where the color passed to .mixin was lightened. If the value of @switch was dark, the result would be a darker color.

Here’s what happened:

• The first mixin definition didn’t match because it expected dark as the first argument.
• The second mixin definition matched, because it expected light.
• The third mixin definition matched because it expected any value.

Only mixin definitions which matched were used. Variables match and bind to any value. Anything other than a variable matches only with a value equal to itself.

We can also match on arity, here’s an example:

.mixin (@a) {
  color: @a;
}
.mixin (@a; @b) {
  color: fade(@a; @b);
}

Now if we call .mixin with a single argument, we will get the output of the first definition, but if we call it with two arguments, we will get the second definition, namely @a faded to @b.

Guards

Guards are useful when you want to match on expressions, as opposed to simple values or arity. If you are familiar with functional programming, you have probably encountered them already.

In trying to stay as close as possible to the declarative nature of CSS, LESS has opted to implement conditional execution via guarded mixins instead of if/else statements, in the vein of @media query feature specifications.

Let’s start with an example:

.mixin (@a) when (lightness(@a) >= 50%) {
  background-color: black;
}
.mixin (@a) when (lightness(@a) < 50%) {
  background-color: white;
}
.mixin (@a) {
  color: @a;
}

The key is the when keyword, which introduces a guard sequence (here with only one guard). Now if we run the following code:

.class1 { .mixin(#ddd) }
.class2 { .mixin(#555) }

Here’s what we’ll get:

.class1 {
  background-color: black;
  color: #ddd;
}
.class2 {
  background-color: white;
  color: #555;
}

The full list of comparison operators usable in guards are: > >= = =< <. Additionally, the keyword true is the only truthy value, making these two mixins equivalent:

.truth (@a) when (@a) { ... }
.truth (@a) when (@a = true) { ... }

Any value other than the keyword true is falsy:

.class {
  .truth(40); // Will not match any of the above definitions.
}

Guards can be separated with a comma ‘,’–if any of the guards evaluates to true, it’s considered as a match:

.mixin (@a) when (@a > 10), (@a < -10) { ... }

Note that you can also compare arguments with each other, or with non-arguments:

@media: mobile;

.mixin (@a) when (@media = mobile) { ... }
.mixin (@a) when (@media = desktop) { ... }

.max (@a; @b) when (@a > @b) { width: @a }
.max (@a; @b) when (@a < @b) { width: @b }

Lastly, if you want to match mixins based on value type, you can use the is* functions:

.mixin (@a; @b: 0) when (isnumber(@b)) { ... }
.mixin (@a; @b: black) when (iscolor(@b)) { ... }

Here are the basic type checking functions:

• iscolor
• isnumber
• isstring
• iskeyword
• isurl

If you want to check if a value, in addition to being a number, is in a specific unit, you may use one of:

• ispixel
• ispercentage
• isem
• isunit

Last but not least, you may use the and keyword to provide additional conditions inside a guard:

.mixin (@a) when (isnumber(@a)) and (@a > 0) { ... }

And the not keyword to negate conditions:

.mixin (@b) when not (@b > 0) { ... }

Nested rules

LESS gives you the ability to use nesting instead of, or in combination with cascading. Lets say we have the following CSS:

#header { color: black; }
#header .navigation {
  font-size: 12px;
}
#header .logo {
  width: 300px;
}
#header .logo:hover {
  text-decoration: none;
}

In LESS, we can also write it this way:

#header {
  color: black;

  .navigation {
    font-size: 12px;
  }
  .logo {
    width: 300px;
    &:hover { text-decoration: none }
  }
}

Or this way:

#header        { color: black;
  .navigation  { font-size: 12px }
  .logo        { width: 300px;
    &:hover    { text-decoration: none }
  }
}

The resulting code is more concise, and mimics the structure of your DOM tree.

Notice the & combinator - it’s used when you want a nested selector to be concatenated to its parent selector, instead of acting as a descendant. This is especially important for pseudo-classes like :hover and :focus.

For example:

.bordered {
  &.float {
    float: left;
  }
  .top {
    margin: 5px;
  }
}

Will output

.bordered.float {
  float: left;
}
.bordered .top {
  margin: 5px;
}

Nested Media Queries

Media queries can be nested in the same way as selectors e.g.

.one {
    @media (width: 400px) {
        font-size: 1.2em;
        @media print and color {
            color: blue;
        }
    }
}

Will output

@media (width: 400px) {
  .one {
    font-size: 1.2em;
  }
}
@media (width: 400px) and print and color {
  .one {
    color: blue;
  }
}

Advanced Usage of &

The & symbol can be used in selectors in order to reverse the ordering of the nesting and to multiply classes.

For example:

.child, .sibling {
    .parent & {
        color: black;
    }
    & + & {
        color: red;
    }
}

Will output

.parent .child,
.parent .sibling {
    color: black;
}
.child + .child,
.child + .sibling,
.sibling + .child,
.sibling + .sibling {
    color: red;
}

You can also use & in mixins in order to reference nesting that is outside of your mixin.

Extend

As of version 1.4, LESS supports extending a style. Extend is sort of like the opposite of a mixin. Instead of adding all the properties of a mixed-in class into a class, it adds the extending selector to the selector list for output of the extended class.

The syntax for extend is designed to mimic the syntax of CSS pseudo-classes, and can be combined with pseudo-classes as long as any extends selectors come last.

For example:

div {
    background-color: #e0e0e0;
}
p:extend(div) {
    color: #101010;
}

Will output

div,
p{
    background-color: #e0e0e0;
}
p{
    color: #101010;
}

As you may have noticed, this can significantly remove the amount of bloat in the output CSS compared to mixins.

The extend selector can be used on the same line as the class selector, or it can be nested as seen in this example:

.parent {
    font-size:12pt;
}
.child {
    &:extend(.parent);
}

By default, extend does not include nested elements of the extended style. To do this, you must add all to the selector in the extend expression.

For example:

.a.b.test,
.test.c {
    color: orange;
}
.test {
  &:hover {
    color: green;
    }
}
.replacement :extend(.test) {
}

Outputs:

.a.b.test,
.test.c {
    color: orange;
}
.test:hover {
    color: green;
}

But this:

.a.b.test,
.test.c {
    color: orange;
}
.test {
  &:hover {
    color: green;
    }
}
.replacement :extend(.test all) {
}

Outputs:

.a.b.test,
.test.c,
.a.b.replacement,
.replacement.c {
  color: orange;
}
.test:hover,
.replacement:hover {
  color: green;
}

Operations

Any number, color or variable can be operated on. Operations should be performed within parentheses. Here are a couple of examples:

@base: 5%;
@filler: (@base * 2);
@other: (@base + @filler);

color: (#888 / 4);
background-color: (@base-color + #111);
height: (100% / 2 + @filler);

The output is pretty much what you expect—LESS understands the difference between colors and units. If a unit is used in an operation, like in:

@var: (1px + 5);

LESS will use that unit for the final output—6px in this case.

Extra parentheses are also authorized in operations:

width: ((@var + 5) * 2);

Functions

LESS provides a variety of functions which transform colors, manipulate strings and do maths. They are documented fully in the function reference.

Using them is pretty straightforward. The following example uses percentage to convert 0.5 to 50%, increases the saturation of a base color by 5% and then sets the background color to one that is lightened by 25% and spun by 8 degrees:

@base: #f04615;
@width: 0.5;

.class {
  width: percentage(0.5); // returns `50%`
  color: saturate(@base, 5%);
  background-color: spin(lighten(@base, 25%), 8);
}

Namespaces

Sometimes, you may want to group your variables or mixins, for organizational purposes, or just to offer some encapsulation. You can do this pretty intuitively in LESS—say you want to bundle some mixins and variables under #bundle, for later re-use, or for distributing:

#bundle {
  .button () {
    display: block;
    border: 1px solid black;
    background-color: grey;
    &:hover { background-color: white }
  }
  .tab { ... }
  .citation { ... }
}

Now if we want to mixin the .button class in our #header a, we can do:

#header a {
  color: orange;
  #bundle > .button;
}

You can “unlock” nested mixins into namespace by calling their owner mixin. Since nested mixins act as return values, all nested mixins are copied into namespace and available from there:

.unlock(@value) { // outer mixin
  .doSomething() { // nested mixin
    declaration: @value;
  }
}

#namespace() {
  .unlock(5); // unlock doSomething mixin
}

#use-namespace { 
  #namespace > .doSomething(); // it works also with namespaces
}

Compiles into:

#use-namespace {
  declaration: 5;
}

Scope

Scope in LESS is very similar to that of programming languages. Variables and mixins are first looked up locally, and if they aren’t found, the compiler will look in the parent scope, and so on.

@var: red;

#page {
  @var: white;
  #header {
    color: @var; // white
  }
}

#footer {
  color: @var; // red
}

Comments

CSS-style comments are preserved by LESS:

/* Hello, I'm a CSS-style comment */
.class { color: black }

Single-line comments are also valid in LESS, but they are ‘silent’, they don’t show up in the compiled CSS output:

// Hi, I'm a silent comment, I won't show up in your CSS
.class { color: white }

Importing

You can import both CSS and LESS files. Only LESS files import statements are processed, CSS file import statements are kept as they are. If you want to import a CSS file, and don’t want LESS to process it, just use the .css extension:

@import "lib.css";

Compilation makes only one change to CSS file imports: top level CSS file imports are moved on top of the sheet, right after @charset declarations.

Input file with import statement:

h1 { color: green; }
@import "import/official-branding.css?urlParameter=23";

import statement has been moved on top:

@import "import/official-branding.css?urlParameter=23";
h1 { color: green; }

Content of imported LESS file is copied into importing style sheet and compiled together with it. Importing and imported files share all mixins, namespaces, variables and other structures.

In addition, if the import statement has media queries specified in it, imported content is enclosed in the @Media declaration.

Imported “library.less”:

@imported-color: red;
h1 { color: green; }

Main file imports the above library.less file:

@import "library.less" screen and (max-width: 400px); // import with media queries
@import "library.less"; // import without media queries

.class {
  color: @importedColor; // use imported variable
}

Compiled output:

// Corresponds to import with media queries
@media screen and (max-width: 400px) {
  h1 { color: green; }
}

// Corresponds to import without media queries
h1 { color: green; }
.class {
  // Use imported variable
  color: #ff0000;
}

LESS file import statement does not have to be located on top of the style sheet. It can be placed also inside rulesets, mixins or other LESS structures.

Import into ruleset:

pre {
  @import "library.less";
  color: @importedColor;
}

both variable and ruleset defined in “library.less” have been copied into the pre ruleset:

pre {
  color: #ff0000; // variable defined in library.less was available
}
pre h1 { // ruleset defined in library.less was nested into 'pre' ruleset
  color: green;
}

In v1.3.0 - v1.3.3 @import imports a file multiple times and you can override this behaviour with @import-once.

In v1.4.0 @import-once has been removed and @import imports once by default. This means that with the following

@import “file.less”; @import “file.less”;

The second file is ignored.

Any file that does not end with .css is considered less file and processed. In addition, if the file name has no extension or parameters, the “.less” suffix is added on the end. Both of these are equivalent:

@import "lib.less";
@import "lib";

In v1.4.0 you can force a file to be interpreted as a particular type by specifying an option, e.g.

@import (css) "lib";

Will output..

@import "lib";

and

@import (less) "lib.css";

Will import the lib.css file and treat it as less. If you specify a file is less and do not include an extension, none will be added.

String interpolation

Variables can be embedded inside strings in a similar way to Ruby or PHP, with the @{name} construct:

@base-url: "http://assets.fnord.com";
background-image: url("@{base-url}/images/bg.png");

Escaping

Sometimes you might need to output a CSS value which is either not valid CSS syntax, or uses proprietary syntax which LESS doesn’t recognize.

To output such value, we place it inside a string prefixed with ~, for example:

.class {
  filter: ~"ms:alwaysHasItsOwnSyntax.For.Stuff()";
}

This is called an “escaped value”, which will result in:

.class {
  filter: ms:alwaysHasItsOwnSyntax.For.Stuff();
}

Escaped values can use the interpolation exactly the same way as strings:

.class {
  @what: "Stuff";
  filter: ~"ms:alwaysHasItsOwnSyntax.For.@{what}()";
}

Selector Interpolation

If you want to use LESS variables inside selectors, you can do this by referencing the variable using @{selector} as in string interpolation. For example:

@name: blocked;
.@{name} {
    color: black;
}

will output

.blocked {
    color: black;
}

Note: prior to LESS 1.3.1 a (~"@{name}") type of selector was supported. Support for this will be removed in 1.4.0.

Media Queries as Variables

If you want to use less variables inside media, you can do this using the usual variable variable referencing syntax @variable. For example:

@singleQuery: ~"(max-width: 500px)";
@media screen, @singleQuery {
  set {
    padding: 3 3 3 3;
  }
}

compiles into:

@media screen, (max-width: 500px) {
  set {
    padding: 3 3 3 3;
  }
}

The variable must contain whole media query. This would cause an error: @media screen and @partial {.

In 1.4.0, without strict maths off, you can also include variables in media values, e.g. @media screen, (max-width: @width) {.

JavaScript evaluation

JavaScript expressions can be evaluated as values inside .less files. We recommend using caution with this feature as the LESS will not be compilable by ports and it makes the LESS harder to maintain. If possible, try to think of a function that can be added to achieve the same purpose and ask for it on github. We have plans to allow expanding the default functions available. However, if you still want to use JavaScript in .less, this is done by wrapping the expression with back-ticks:

@var: `"hello".toUpperCase() + '!'`;

Becomes:

@var: "HELLO!";

Note that you may also use interpolation and escaping as with strings:

@str: "hello";
@var: ~`"@{str}".toUpperCase() + '!'`;

Becomes:

@var: HELLO!;

It is also possible to access the JavaScript environment:

@height: `document.body.clientHeight`;

If you want to parse a JavaScript string as a hex color, you may use the color function:

@color: color(`window.colors.baseColor`);
@darkcolor: darken(@color, 10%);

Index

escape(@string);               // URL encodes a string
e(@string);                    // escape string content
%(@string, values...);         // formats a string

unit(@dimension, [@unit: ""]); // remove or change the unit of a dimension
color(@string);                // parses a string to a color
data-uri([mimetype,] url);       // * inlines a resource and falls back to url()

ceil(@number);                 // rounds up to an integer
floor(@number);                // rounds down to an integer
percentage(@number);           // converts to a %, e.g. 0.5 -> 50%
round(number, [places: 0]);    // rounds a number to a number of places
sqrt(number);                  // * calculates square root of a number
abs(number);                   // * absolute value of a number
sin(number);                   // * sine function
asin(number);                  // * arcsine - inverse of sine function
cos(number);                   // * cosine function
acos(number);                  // * arccosine - inverse of cosine function
tan(number);                   // * tangent function
atan(number);                  // * arctangent - inverse of tangent function
pi();                          // * returns pi
pow(@base, @exponent);     // * first argument raised to the power of the second argument
mod(number, number);       // * first argument modulus second argument

convert(number, units);    // * converts between number types
unit(number, units);       // *changes number units without converting it
color(string);             // converts string or escaped value into color

rgb(@r, @g, @b);                             // converts to a color
rgba(@r, @g, @b, @a);                        // converts to a color
argb(@color);                                // creates a #AARRGGBB
hsl(@hue, @saturation, @lightness);          // creates a color
hsla(@hue, @saturation, @lightness, @alpha); // creates a color
hsv(@hue, @saturation, @value);              // creates a color
hsva(@hue, @saturation, @value, @alpha);     // creates a color

hue(@color);           // returns the `hue` channel of @color in the HSL space
saturation(@color);    // returns the `saturation` channel of @color in the HSL space
lightness(@color);     // returns the 'lightness' channel of @color in the HSL space
hsvhue(@color);        // * returns the `hue` channel of @color in the HSV space
hsvsaturation(@color); // * returns the `saturation` channel of @color in the HSV space
hsvvalue(@color);      // * returns the 'value' channel of @color in the HSV space
red(@color);           // returns the 'red' channel of @color
green(@color);         // returns the 'green' channel of @color
blue(@color);          // returns the 'blue' channel of @color
alpha(@color);         // returns the 'alpha' channel of @color
luma(@color);          // returns the 'luma' value (perceptual brightness) of @color

saturate(@color, 10%);                  // return a color 10% points *more* saturated
desaturate(@color, 10%);                // return a color 10% points *less* saturated
lighten(@color, 10%);                   // return a color 10% points *lighter*
darken(@color, 10%);                    // return a color 10% points *darker*
fadein(@color, 10%);                    // return a color 10% points *less* transparent
fadeout(@color, 10%);                   // return a color 10% points *more* transparent
fade(@color, 50%);                      // return @color with 50% transparency
spin(@color, 10);                       // return a color with a 10 degree larger in hue
mix(@color1, @color2, [@weight: 50%]);  // return a mix of @color1 and @color2
tint(@color, 10%);                      // return a color mixed 10% with white
shade(@color, 10%);                     // return a color mixed 10% with black
greyscale(@color);                      // returns a grey, 100% desaturated color
contrast(@color1, [@darkcolor: black], [@lightcolor: white], [@threshold: 43%]); 
                                        // return @darkcolor if @color1 is > 43% luma
                                        // otherwise return @lightcolor, see notes

multiply(@color1, @color2);
screen(@color1, @color2);
overlay(@color1, @color2);
softlight(@color1, @color2);
hardlight(@color1, @color2);
difference(@color1, @color2);
exclusion(@color1, @color2);
average(@color1, @color2);
negation(@color1, @color2);

iscolor(@colorOrAnything);              // returns true if passed a color, including keyword colors
isnumber(@numberOrAnything);            // returns true if a number of any unit
isstring(@stringOrAnything);            // returns true if it is passed a string
iskeyword(@keywordOrAnything);          // returns true if it is passed keyword
isurl(@urlOrAnything);                  // returns true if it is a string and a url
ispixel(@pixelOrAnything);              // returns true if it is a number and a px
ispercentage(@percentageOrAnything);    // returns true if it is a number and a %
isem(@emOrAnything);                    // returns true if it is a number and an em
isunit(@numberOrAnything, "rem");       // * returns if a parameter is a number and is in a particular unit

// * These functions are only available in the 1.4.0 beta

String functions

escape

Applies URL-encoding to special characters found in the input string.

• Following characters are exceptions and not encoded: ,, /, ?, @, &, +, ', ~, ! and $.
• Most common encoded characters are: <space>, #, ^, (, ), {, }, |, :, >, <, ;, ], [ and =.

Parameters:

• string: A string to escape

Returns: escaped string content without quotes.

Example:

escape('a=1')

Output:

a%3D1

Note: Function behavior if a parameter is non-string parameters is not defined. Current implementation returns undefined on color and unchanged input on any other kind of argument. This behaviour should not be relied on and can change in the future.

e

CSS escaping similar to ~"value" syntax. It expects string as a parameter and return its content as is, but without quotes. It can be used to output CSS value which is either not valid CSS syntax, or uses proprietary syntax which LESS doesn�t recognize.

Parameters:

• string: A string to escape

Returns: string content without quotes.

Example:

filter: ~"ms:alwaysHasItsOwnSyntax.For.Stuff()";

Output:

filter: ms:alwaysHasItsOwnSyntax.For.Stuff();

Note: The function accepts also ~"" escaped values and numbers as parameters. Anything else returns an error.

% format

The function %("format", arguments ...) formats a string. The first argument is string with placeholders. All placeholders start with percentage symbol % followed by letter s,S,d,D,a, or A. Remaining arguments contain expressions to replace placeholders. If you need to print the percentage symbol, escape it by another percentage %%.

Use uppercase placeholders if you need to escape special characters into their utf-8 escape codes. The function escapes all special characters except ()'~!. Space is encoded as %20. Lowercase placeholders leave special characters as they are.

Placeholders: * d, D, a, A - can be replaced by any kind of argument (color, number, escaped value, expression, …). If you use them in combination with string, the whole string will be used - including its quotes. However, the quotes are placed into the string as they are, they are not escaped by “/” nor anything similar. * s, S - can be replaced by any kind of argument except color. If you use them in combination with string, only the string value will be used - string quotes are omitted.

Parameters:

• string: format string with placeholders,
• anything* : values to replace placeholders.

Returns: formatted string.

Example:

format-a-d: %("repetitions: %a file: %d", 1 + 2, "directory/file.less");
format-a-d-upper: %('repetitions: %A file: %D', 1 + 2, "directory/file.less");
format-s: %("repetitions: %s file: %s", 1 + 2, "directory/file.less");
format-s-upper: %('repetitions: %S file: %S', 1 + 2, "directory/file.less");

Output:

format-a-d: "repetitions: 3 file: "directory/file.less"";
format-a-d-upper: "repetitions: 3 file: %22directory%2Ffile.less%22";
format-s: "repetitions: 3 file: directory/file.less";
format-s-upper: "repetitions: 3 file: directory%2Ffile.less";

Misc functions

color

Parses a color, so a string representing a color becomes a color.

Parameters:

• string: A string of the color

Example:

color("#aaa");

Output:

#aaa

unit

Remove or change the unit of a dimension

Parameters:

• dimension: A number, with or without a dimension
• unit: Optional: the unit to change to, or if omitted it will remove the unit

Example:

unit(5, px)

Output:

5px

Example:

unit(5em)

Output:

5

data-uri

Inlines a resource and falls back to url() if the ieCompat option is on and the resource is too large, or if you use the function in the browser. If the mime is not given then node uses the mime package to determine the correct mime type.

Parameters:

• mimetype: A mime type string. Optional.
• url: The URL of the file to inline.

Example:

data-uri('../data/image.jpg');

Output:

url('data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==');

Output in the browser:

url('../data/image.jpg');

Example:

data-uri('image/jpeg;base64', '../data/image.jpg');

Output:

url('data:image/jpeg;base64,bm90IGFjdHVhbGx5IGEganBlZyBmaWxlCg==');

Math functions

ceil

Rounds up to the next highest integer.

Parameters:

• number: A floating point number.

Returns: integer

Example:

ceil(2.4)

Output:

3

floor

Rounds down to the next lowest integer.

Parameters:

• number: A floating point number.

Returns: integer

Example:

floor(2.6)

Output:

2

percentage

Converts a floating point number into a percentage string.

Parameters:

• number: A floating point number.

Returns: string

Example:

percentage(0.5)

Output:

50%

round

Applies rounding.

Parameters:

• number: A floating point number.
• decimalPlaces: Optional: The number of decimal places to round to. Defaults to 0.

Returns: number

Example:

round(1.67)

Output:

2

Example:

round(1.67, 1)

Output:

1.7

sqrt

Calculates square root of a number. Keeps units as they are.

Parameters:

• number: A floating point number.

Returns: number

Example:

sqrt(25cm)

Output:

5cm

Example:

sqrt(18.6%)

Output:

4.312771730569565%;

abs

Calculates absolute value of a number. Keeps units as they are.

Parameters:

• number: A floating point number.

Returns: number

Example:

abs(25cm)

Output:

25cm

Example:

abs(-18.6%)

Output:

18.6%;

sin

Calculates sine function. Assumes radians on numbers without units.

Parameters:

• number: A floating point number.

Returns: number

Example:

sin(1); // sine of 1 radian
sin(1deg); // sine of 1 degree
sin(1grad); // sine of 1 gradian

Output:

0.8414709848078965; // sine of 1 radian
0.01745240643728351; // sine of 1 degree
0.015707317311820675; // sine of 1 gradian

asin

Calculates arcsine (inverse of sine) function. Returns number in radians e.g. a number between -π/2 and π/2.

Parameters:

• number: A floating point number from [-1, 1] interval.

Returns: number

Example:

asin(-0.8414709848078965)
asin(0) 
asin(2)

Output:

-1rad
0rad
NaNrad

cos

Calculates cosine function. Assumes radians on numbers without units.

Parameters:

• number: A floating point number.

Returns: number

Example:

cos(1) // cosine of 1 radian
cos(1deg) // cosine of 1 degree
cos(1grad) // cosine of 1 gradian

Output:

0.5403023058681398 // cosine of 1 radian
0.9998476951563913 // cosine of 1 degree
0.9998766324816606 // cosine of 1 gradian

acos

Calculates arccosine (inverse of cosine) function. Returns number in radians e.g. a number between 0 and π.

Parameters:

• number: A floating point number from [-1, 1] interval.

Returns: number

Example:

acos(0.5403023058681398)
acos(1) 
acos(2)

Output:

1rad
0rad
NaNrad

tan

Calculates tangent function. Assumes radians on numbers without units.

Parameters:

• number: A floating point number.

Returns: number

Example:

tan(1) // tangent of 1 radian
tan(1deg) // tangent of 1 degree
tan(1grad) // tangent of 1 gradian

Output:

1.5574077246549023 // tangent of 1 radian
0.017455064928217585 // tangent of 1 degree
0.015709255323664916 // tangent of 1 gradian

atan

Calculates arctangent (inverse of tangent) function. Returns number in radians e.g. a number between -π/2 and π/2.

Parameters:

• number: A floating point number.

Returns: number

Example:

atan(-1.5574077246549023)
atan(0)
round(atan(22), 6) // arctangent of 22 rounded to 6 decimal places

Output:

-1rad
0rad
1.525373rad;

pi

Returns π (pi);

Parameters:

• none

Returns: number

Example:

pi()

Output:

3.141592653589793

pow

Returns the value of the first argument raised to the power of the second argument. Returned value has the same dimension as the first parameter and the dimension of the second parameter is ignored.

Parameters:

• number: base -a floating point number.
• number: exponent - a floating point number.

Returns: number

Example:

pow(0cm, 0px)
pow(25, -2)
pow(25, 0.5)
pow(-25, 0.5)
pow(-25%, -0.5)

Output:

1cm
0.0016
5
NaN
NaN%

mod

Returns the value of the first argument modulus second argument. Returned value has the same dimension as the first parameter, the dimension of the second parameter is ignored. The function is able to handle also negative and floating point numbers.

Parameters:

• number: a floating point number.
• number: a floating point number.

Returns: number

Example:

mod(0cm, 0px)
mod(11cm, 6px);
mod(-26%, -5);

Output:

NaNcm;
5cm
-1%;

convert

Converts numbers from one type into another. First argument contains number with units and second argument contains units. If both units are compatible, the number is converted. If they are not compatible, function returns first argument without modifying it.

Compatible unit groups: * lengths: m, cm, mm, in, pt and pc, * time: s and ms, * angle: rad, deg, grad and turn.

Parameters:

• number: a floating point number with units.
• identifier, string or escaped value: units

Returns: number

Example:

convert(9s, "ms")
convert(14cm, mm)
convert(8, mm) // incompatible unit types

Output:

9000ms
140mm
8

Unit

Returns number with different units. Only units are changed, number itself is not converted. The function assumes that second parameter contains valid unit type.

Parameters:

• number: a floating point number with units.
• identifier or escaped value: units.

Returns: number

Example:

unit(9s, ~"ms")
unit(-9, m)

Output:

9ms
-9m

Color

Converts a string or escaped value into a color. The input must contain color in hexadecimal or shorthand representation.

Parameters:

• identifier or escaped value with valid color in hexadecimal or shorthand representation.

Returns: color

Example:

color("#445566")
color(~"#123")

Output:

#445566
#112233

Color functions

Color definition

rgb

Creates an opaque color object from decimal red, green and blue (RGB) values. Literal color values in standard HTML/CSS formats may also be used to define colors, for example #ff0000.

Parameters:

• red: An integer 0-255 or percentage 0-100%.
• green: An integer 0-255 or percentage 0-100%.
• blue: An integer 0-255 or percentage 0-100%.

Returns: color

Example:

rgb(90, 129, 32)

Output:

#5a8120

rgba

Creates a transparent color object from decimal red, green, blue and alpha (RGBA) values.

Parameters:

• red: An integer 0-255 or percentage 0-100%.
• green: An integer 0-255 or percentage 0-100%.
• blue: An integer 0-255 or percentage 0-100%.
• alpha: An number 0-1 or percentage 0-100%.

Returns: color

Example:

rgba(90, 129, 32, 0.5)

Output:

rgba(90, 129, 32, 0.5)

argb

Creates a hex representation of a color in #AARRGGBB format (NOT #RRGGBBAA!). This format is used in Internet Explorer, and .NET and Android development.

Parameters:

• color: A color object.

Returns: string

Example:

argb(rgba(90, 23, 148, 0.5));

Output:

#805a1794

hsl

Creates an opaque color object from hue, saturation and lightness (HSL) values.

Parameters:

• hue: An integer 0-360 representing degrees.
• saturation: A percentage 0-100% or number 0-1.
• lightness: A percentage 0-100% or number 0-1.

Returns: color

Example:

hsl(90, 100%, 50%)

Output:

#80ff00

This is useful if you want to create a new color based on another color’s channel, for example:

@new: hsl(hue(@old), 45%, 90%);

@new will have @old’s hue, and its own saturation and lightness.

hsla

Creates a transparent color object from hue, saturation, lightness and alpha (HSLA) values.

Parameters:

• hue: An integer 0-360 representing degrees.
• saturation: A percentage 0-100% or number 0-1.
• lightness: A percentage 0-100% or number 0-1.
• alpha: A percentage 0-100% or number 0-1.

Returns: color

Example:

hsl(90, 100%, 50%, 0.5)

Output:

rgba(128, 255, 0, 0.5)

hsv

Creates an opaque color object from hue, saturation and value (HSV) values. Note that this is not the same as hsl, and is a color space available in Photoshop.

Parameters:

• hue: An integer 0-360 representing degrees.
• saturation: A percentage 0-100% or number 0-1.
• value: A percentage 0-100% or number 0-1.

Returns: color

Example:

hsv(90, 100%, 50%)

Output:

#408000

hsva

Creates a transparent color object from hue, saturation, value and alpha (HSVA) values. Note that this is not the same as hsla, and is a color space available in Photoshop.

Parameters:

• hue: An integer 0-360 representing degrees.
• saturation: A percentage 0-100% or number 0-1.
• value: A percentage 0-100% or number 0-1.
• alpha: A percentage 0-100% or number 0-1.

Returns: color

Example:

hsva(90, 100%, 50%, 0.5)

Output:

rgba(64, 128, 0, 0.5)

Color channel information

hue

Extracts the hue channel of a color object.

Parameters:

• color: A color object.

Returns: integer 0-360

Example:

hue(hsl(90, 100%, 50%))

Output:

90

saturation

Extracts the saturation channel of a color object.

Parameters:

• color: A color object.

Returns: percentage 0-100

Example:

saturation(hsl(90, 100%, 50%))

Output:

100%

lightness

Extracts the lightness channel of a color object.

Parameters:

• color: A color object.

Returns: percentage 0-100

Example:

lightness(hsl(90, 100%, 50%))

Output:

50%

hsvhue

Extracts the hue channel of a color object in the HSV color space.

Parameters:

• color: A color object.

Returns: integer 0-360

Example:

hsvhue(hsv(90, 100%, 50%))

Output:

90

hsvsaturation

Extracts the saturation channel of a color object in the HSV color space.

Parameters:

• color: A color object.

Returns: percentage 0-100

Example:

hsvsaturation(hsv(90, 100%, 50%))

Output:

100%

hsvvalue

Extracts the value channel of a color object in the HSV color space.

Parameters:

• color: A color object.

Returns: percentage 0-100

Example:

hsvvalue(hsv(90, 100%, 50%))

Output:

50%

red

Extracts the red channel of a color object.

Parameters:

• color: A color object.

Returns: integer 0-255

Example:

red(rgb(10, 20, 30))

Output:

10

green

Extracts the green channel of a color object.

Parameters:

• color: A color object.

Returns: integer 0-255

Example:

green(rgb(10, 20, 30))

Output:

20

blue

Extracts the blue channel of a color object.

Parameters:

• color: A color object.

Returns: integer 0-255

Example:

blue(rgb(10, 20, 30))

Output:

30

alpha

Extracts the alpha channel of a color object.

Parameters:

• color: A color object.

Returns: float 0-1

Example:

alpha(rgba(10, 20, 30, 0.5))

Output:

0.5

luma

Calculates the luma) (perceptual brightness) of a color object. Uses SMPTE C / Rec. 709 coefficients, as recommended in WCAG 2.0. This calculation is also used in the contrast function.

Parameters:

• color: A color object.

Returns: percentage 0-100%

Example:

luma(rgb(100, 200, 30))

Output:

65%

Color operations

Color operations generally take parameters in the same units as the values they are changing, and percentage are handled as absolutes, so increasing a 10% value by 10% results in 20%, not 11%, and values are clamped to their allowed ranges; they do not wrap around. Where return values are shown, we’ve also shown formats that make it clear what each function has done, in addition to the hex versions that you will usually be be working with.

saturate

Increase the saturation of a color by an absolute amount.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

saturate(hsl(90, 90%, 50%), 10%)

Output:

#80ff00 // hsl(90, 100%, 50%)

desaturate

Decrease the saturation of a color by an absolute amount.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

desaturate(hsl(90, 90%, 50%), 10%)

Output:

#80e51a // hsl(90, 80%, 50%)

lighten

Increase the lightness of a color by an absolute amount.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

lighten(hsl(90, 90%, 50%), 10%)

Output:

#99f53d // hsl(90, 90%, 60%)

darken

Decrease the lightness of a color by an absolute amount.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

darken(hsl(90, 90%, 50%), 10%)

Output:

#66c20a // hsl(90, 90%, 40%)

fadein

Decrease the transparency (or increase the opacity) of a color, making it more opaque. Has no effect on opaque colours. To fade in the other direction use fadeout.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

fadein(hsla(90, 90%, 50%, 0.5), 10%)

Output:

rgba(128, 242, 13, 0.6) // hsla(90, 90%, 50%, 0.6)

fadeout

Increase the transparency (or decrease the opacity) of a color, making it less opaque. To fade in the other direction use fadein.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

fadeout(hsla(90, 90%, 50%, 0.5), 10%)

Output:

rgba(128, 242, 13, 0.4) // hsla(90, 90%, 50%, 0.6)

fade

Set the absolute transparency of a color. Can be applied to colors whether they already have an opacity value or not.

Parameters:

• color: A color object.
• amount: A percentage 0-100%.

Returns: color

Example:

fade(hsl(90, 90%, 50%), 10%)

Output:

rgba(128, 242, 13, 0.1) //hsla(90, 90%, 50%, 0.1)

spin

Rotate the hue angle of a color in either direction. While the angle range is 0-360, it applies a mod 360 operation, so you can pass in much larger (or negative) values and they will wrap around e.g. angles of 360 and 720 will produce the same result. Note that colours are passed through an RGB conversion, which doesn’t retain hue value for greys (because hue has no meaning when there is no saturation), so make sure you apply functions in a way that preserves hue, for example don’t do this:

@c: saturate(spin(#aaaaaa, 10), 10%);

Do this instead:

@c: spin(saturate(#aaaaaa, 10%), 10);

Colors are always returned as RGB values, so applying spin to a grey value will do nothing.

Parameters:

• color: A color object.
• angle: A number of degrees to rotate (+ or -).

Returns: color

Example:

spin(hsl(10, 90%, 50%), 20)
spin(hsl(10, 90%, 50%), -20)

Output:

#f27f0d // hsl(30, 90%, 50%)
#f20d33 // hsl(350, 90%, 50%)

mix

Mix two colors together in variable proportion. Opacity is included in the calculations.

Parameters:

• color1: A color object.
• color1: A color object.
• weight: Optional, a percentage balance point between the two colors, defaults to 50%.

Returns: color

Example:

mix(#ff0000, #0000ff, 50%)
mix(rgba(100,0,0,1.0), rgba(0,100,0,0.5), 50%)

Output:

#800080
rgba(75, 25, 0, 0.75)

greyscale

Remove all saturation from a color; the same as calling desaturate(@color, 100%). Because the saturation is not affected by hue, the resulting color mapping may be somewhat dull or muddy; luma may provide a better result as it extracts perceptual rather than linear brightness, for example greyscale('#0000ff') will return the same value as greyscale('#00ff00'), though they appear quite different in brightness to the human eye.

Parameters:

• color: A color object.

Returns: color

Example:

greyscale(hsl(90, 90%, 50%))

Output:

#808080 // hsl(90, 0%, 50%)

contrast

Choose which of two colors provides the greatest contrast with another. This is useful for ensuring that a color is readable against a background, which is also useful for accessibility compliance. This function works the same way as the contrast function in Compass for SASS. In accordance with WCAG 2.0, colors are compared using their luma value, not their lightness.

The light and dark parameters can be supplied in either order - the function will calculate their luma values and assign light and dark appropriately.

Parameters:

• color: A color object to compare against.
• dark: optional - A designated dark color (defaults to black).
• light: optional - A designated light color (defaults to white).
• threshold: optional - A percentage 0-100% specifying where the transition from “dark” to “light” is (defaults to 43%). This is used to bias the contrast one way or another, for example to allow you to decide whether a 50% grey background should result in black or white text. You would generally set this lower for ‘lighter’ palettes, higher for ‘darker’ ones. Defaults to 43%.

Returns: color

Example:

contrast(#aaaaaa)
contrast(#222222, #101010)
contrast(#222222, #101010, #dddddd)
contrast(hsl(90, 100%, 50%),#000000,#ffffff,40%);
contrast(hsl(90, 100%, 50%),#000000,#ffffff,60%);

Output:

#000000 // black
#ffffff // white
#dddddd
#000000 // black
#ffffff // white

Color blending

These operations are similar to the blend modes found in image editors like Photoshop, Fireworks or GIMP, so you can use them to make your CSS colors match your images.

multiply

Multiply two colors. For each two colors their RGB channel are multiplied then divided by 255. The result is a darker color.

Parameters:

• color1: A color object to multiply against.
• color2: A color object to multiply against.

Returns: color

Examples:

multiply(#ff6600, #000000);

multiply(#ff6600, #333333);

multiply(#ff6600, #666666);

multiply(#ff6600, #999999);

multiply(#ff6600, #cccccc);

multiply(#ff6600, #ffffff);

multiply(#ff6600, #ff0000);

multiply(#ff6600, #00ff00);

multiply(#ff6600, #0000ff);

screen

Do the opposite effect from multiply. The result is a brighter color.

Parameters:

• color1: A color object to screen against.
• color2: A color object to screen against.

Returns: color

Example:

screen(#ff6600, #000000);

screen(#ff6600, #333333);

screen(#ff6600, #666666);

screen(#ff6600, #999999);

screen(#ff6600, #cccccc);

screen(#ff6600, #ffffff);

screen(#ff6600, #ff0000);

screen(#ff6600, #00ff00);

screen(#ff6600, #0000ff);

overlay

Combines the effect from both multiply and screen. Conditionally make light channels lighter and dark channels darker. Note: The results of the conditions are determined by the first color parameter.

Parameters:

• color1: A color object to overlay another. Also it is the determinant color to make the result lighter or darker.
• color2: A color object to be overlayed.

Returns: color

Example:

overlay(#ff6600, #000000);

overlay(#ff6600, #333333);

overlay(#ff6600, #666666);

overlay(#ff6600, #999999);

overlay(#ff6600, #cccccc);

overlay(#ff6600, #ffffff);

overlay(#ff6600, #ff0000);

overlay(#ff6600, #00ff00);

overlay(#ff6600, #0000ff);

softlight

Similar to overlay but avoid pure black resulting in pure black, and pure white resulting in pure white.

Parameters:

• color1: A color object to soft light another.
• color2: A color object to be soft lighten.

Returns: color

Example:

softlight(#ff6600, #000000);

softlight(#ff6600, #333333);

softlight(#ff6600, #666666);

softlight(#ff6600, #999999);

softlight(#ff6600, #cccccc);

softlight(#ff6600, #ffffff);

softlight(#ff6600, #ff0000);

softlight(#ff6600, #00ff00);

softlight(#ff6600, #0000ff);

hardlight

Similar to overlay but use the second color to detect light and dark channels instead of using the first color.

Parameters:

• color1: A color object to overlay another.
• color2: A color object to be overlayed. Also it is the determinant color to make the result lighter or darker.

Returns: color

Example:

hardlight(#ff6600, #000000);

hardlight(#ff6600, #333333);

hardlight(#ff6600, #666666);

hardlight(#ff6600, #999999);

hardlight(#ff6600, #cccccc);

hardlight(#ff6600, #ffffff);

hardlight(#ff6600, #ff0000);

hardlight(#ff6600, #00ff00);

hardlight(#ff6600, #0000ff);

difference

Substracts the second color from the first color. The operation is made per RGB channels. The result is a darker color.

Parameters:

• color1: A color object to act as the minuend.
• color2: A color object to act as the subtrahend.

Returns: color

Example:

difference(#ff6600, #000000);

difference(#ff6600, #333333);

difference(#ff6600, #666666);

difference(#ff6600, #999999);

difference(#ff6600, #cccccc);

difference(#ff6600, #ffffff);

difference(#ff6600, #ff0000);

difference(#ff6600, #00ff00);

difference(#ff6600, #0000ff);

exclusion

Similar effect to difference with lower contrast.

Parameters:

• color1: A color object to act as the minuend.
• color2: A color object to act as the subtrahend.

Returns: color

Example:

exclusion(#ff6600, #000000);

exclusion(#ff6600, #333333);

exclusion(#ff6600, #666666);

exclusion(#ff6600, #999999);

exclusion(#ff6600, #cccccc);

exclusion(#ff6600, #ffffff);

exclusion(#ff6600, #ff0000);

exclusion(#ff6600, #00ff00);

exclusion(#ff6600, #0000ff);

average

Compute the average of two colors. The operation is made per RGB channels.

Parameters:

• color1: A color object.
• color2: A color object.

Returns: color

Example:

average(#ff6600, #000000);

average(#ff6600, #333333);

average(#ff6600, #666666);

average(#ff6600, #999999);

average(#ff6600, #cccccc);

average(#ff6600, #ffffff);

average(#ff6600, #ff0000);

average(#ff6600, #00ff00);

average(#ff6600, #0000ff);

negation

Do the opposite effect from difference. The result is a brighter color. Note: The opposite effect doesn’t mean the inverted effect as resulting to an addition operation.

Parameters:

• color1: A color object to act as the minuend.
• color2: A color object to act as the subtrahend.

Returns: color

Example:

negation(#ff6600, #000000);

negation(#ff6600, #333333);

negation(#ff6600, #666666);

negation(#ff6600, #999999);

negation(#ff6600, #cccccc);

negation(#ff6600, #ffffff);

negation(#ff6600, #ff0000);

negation(#ff6600, #00ff00);

negation(#ff6600, #0000ff);