Introduction

This library was designed to be used by another library which generates SVG files. It is currently focused on the small set of basic color manipulations (lightening, compliments, etc) you might use to generate a color palette for a GUI or web page.

It's currently known to work with recent versions of SBCL (on OSX and Linux), LispWorks (OSX), and OpenMCL (OSX).

Examples

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Package

The package name is :simple-rgb, with a single nickname, :rgb.

It depends on no other libraries, but you will need LIFT to run the unit tests.

Conditions and Restarts

condition hsv-type-error

This condition is raised by hsv if any of the three values passed to it falls outside the range 0.0 through 1.0.

There are no restarts.

Functions

function rgb r g b => rgb-vector

This is the only way to create a literal RGB value the rest of the library will accept. Each color element is an integer between 0 and 255. Anything outside this range, or of a non-integer type, will raise a type-error condition.

function rgb= a b => boolean

Tests RGB equality.

function hsv h s v => hsv-vector

This is the only way to create a literal HSV value the rest of the library will accept. Each of the values has to be a float between 0.0 and 1.0. A range or type problem will result in a hsv-type-error condition being raised.

Note that some HSV libraries represent the h element in degrees — this one does not.

function mix-rgb a b &key (alpha 0.5) => rgb-vector

Blends two RGB colors. By default the mix is even, but by setting the :alpha keyword you can weight the mix, with 0.0 simply returning the first argument, 1.0 the second.

function lighten-rgb a => rgb-vector

Lightens a color by mixing it with white with an alpha of 0.5. For different shading use mix-rgb directly.

function darken-rgb a => rgb-vector

Darkens a color by mixing it with black with an alpha of 0.5. For different shading use mix-rgb directly.

function greyscale-rgb a => rgb-vector

Converts a color to greyscale by setting each color element to the value 0.3r + 0.59g + 0.11b. See: Grayscale.

function invert-rgb a => rgb-vector

Inverts a color.

function complement-rgb a => rgb-vector

Creates the complement of the color using the forumla described at Adobe.

function rgb->hsv a => hsv-vector

Converts an RGB value to HSV.

function hsv->rgb a => rgb-vector

Converts and HSV value to RGB.

function rotate-hsv a rotation => hsv-vector

Rotates the hue of a HSV color. The rotation is expressed in degrees, rather than the 0.0-1.0 range used by the rest of the library. Creating palettes of complimentary and contrasting colors is often thought of in terms of rotating a color wheel, and I've used degrees here since that's more natural for me, at least, to think about.

function rotate-rgb a rotation => rgb-vector

This convenience function is equivalent to: (hsv->rgb (rotate-hsv (rgb->hsv a) rotation))

function xmlify-rgb a &optional (stream nil) => x/html-color-string

Turns an RGB value into a string of the form #FFAADD. Optionally you can specify a stream designator of the sort format expects. By default it returns the string.