Reference Manual of the Color Library

A library which contains the basic of handling colors in LAML. The library has encoding functions that convert rgb color lists, such as (rgb-color 255 255 255) and (255 255 255) to a strings, such as "#ffffff". The primary color encoding function is rgb-color-encoding. The primary color representation function is make-rgb-color, which is accompanied by the color predicate rgb-color? a the color selectors red-of-rgb-color, green-of-rgb-color, and blue-of-rgb-color.

Of historical reasons we support two representation of colors. The first - the old representation - is just a list of red, green, blue numbers (positive integers between 0 and 255), such as (255 0 255). The other is a tagged list of red, green, blue values such as (rgb-color 255 0 255), where rgb-color is the tag symbol. Please be aware of the two different representations when you use this library.

The library also contains a set of color constants, all bound to the old color format (of backward compatibility reasons).

aqua	aqua	A color constant.
black	black	A color constant.
blue	blue	A color constant.
blue-of-rgb-color	(blue-of-rgb-color color)	Return the blue constituent of the color.
blue1	blue1	A color constant.
blue2	blue2	A color constant.
blue3	blue3	A color constant.
brown	brown	A color constant.
dark-red	dark-red	A color constant.
dark-yellow	dark-yellow	A color constant.
fuchsia	fuchsia	A color constant.
green	green	A color constant.
green-of-rgb-color	(green-of-rgb-color color)	Return the green constituent of the color.
green1	green1	A color constant.
green2	green2	A color constant.
grey	grey	A color constant.
grey1	grey1	A color constant.
grey2	grey2	A color constant.
light-blue	light-blue	A color constant.
lime	lime	A color constant.
make-color	(make-color r g b)	Make and return the rgb-list representation of the color with r red, g green, and b blue.
make-rgb-color	(make-rgb-color r g b)	Make and return a color represented by a red, green and blue constituent.
maroon	maroon	A color constant.
navy	navy	A color constant.
olive	olive	A color constant.
orange	orange	A color constant.
purple	purple	A color constant.
red	red	A color constant.
red-of-rgb-color	(red-of-rgb-color color)	Return the red constituent of the LAML color.
rgb-color	(rgb-color r g b)	Return an 'Internet color string" encoding the colors r, g, and b.
rgb-color-encoding	(rgb-color-encoding . color-pars)	Return a color encoding (a string of length seven such as "#123456") of color-pars.
rgb-color-list	(rgb-color-list color-triple-list)	Returns the color encoding of (list r g b) given a list of three color numbers as parameter.
rgb-color?	(rgb-color? x)	Is x a LAML color
silver	silver	A color constant.
tetal	tetal	A color constant.
white	white	A color constant.
yellow	yellow	A color constant.

1. Primary color encoding function.	3. Color constructor, predicate, and selectors.
2. Secondary color encoding functions.	4. Color constants.


1 Primary color encoding function.
The function in this section, rgb-color-encoding, accepts a variety of different color formats as input. It returns a string of length seven, such as "#ff00ff". The output format is the primary color representation in most web contexts.

rgb-color-encoding
Form	(rgb-color-encoding . color-pars)
Description	Return a color encoding (a string of length seven such as "#123456") of color-pars. The color-pars parameter(s) to this function are very versatile. If it is a color encoding string already, just return it. If it is a color value which satisfies the predicate rgb-color?, return the encoding of this value. If it is a symbol, return the color encoding bound to it. If it is a string, transform it to a symbol and return the color encoding bound to it. If it is a list like (list 1 2 3), consider it as a red-green-blue list, and return the color encoding of it. If it is three individiual parameters, say r, g, and b, return the color encoding of red r, green g, and blue b. If you care about efficiency, use can consider to use the function rgb-color instead of rgb-color-encoding.
Returns	A string of length 7 of the format "#rrggbb".
Examples	(rgb-color-encoding "red") => "#ff0000"
	(rgb-color-encoding 'red) => "#ff0000"
	(rgb-color-encoding "#ff0000") => "#ff0000"
	(rgb-color-encoding (make-color 255 0 0)) => "#ff0000"
	(rgb-color-encoding '(255 0 0)) => "#ff0000"
	(rgb-color-encoding (make-rgb-color 255 0 0)) => "#ff0000"
	(rgb-color-encoding 255 0 0) => "#ff0000"
See also	Scheme source file	rgb-color-encoding
	more efficient functions	rgb-color rgb-color-list

2 Secondary color encoding functions.
The functions in this section only work with the old version of the color representation. This is the untagged list representation, such as '(255 0 0). For new development, the function make-rgb-color should be used together with the color encoding function rgb-color-encoding.

rgb-color
Form	(rgb-color r g b)
Description	Return an 'Internet color string" encoding the colors r, g, and b.
Parameters	r	The amount of red - a decimal number between 0 and 255.
	g	The amount of green - a decimal number between 0 and 255.
	b	The amount of blue - a decimal number between 0 and 255.
Returns	A string of length 7 of the form "#rrggbb".
Examples	(rgb-color 1 2 3) => "#010203"
	(rgb-color 10 11 12) => "#0a0b0c"
See also	Scheme source file	rgb-color

rgb-color-list
Form	(rgb-color-list color-triple-list)
Description	Returns the color encoding of (list r g b) given a list of three color numbers as parameter.
Parameters	color-triple-list	A list of length 3. Each element of the list is a decimal integer between 0 and 255.
Returns	A string of length 7 of the form "#rrggbb".
Examples	(rgb-color-list (list 1 2 3)) => "#010203"
	(rgb-color-list (list 10 11 12)) => "#0a0b0c"
See also	Scheme source file	rgb-color-list

3 Color constructor, predicate, and selectors.
The function make-rgb-color is the primary color constructor in LAML-based software. The predidate and the selectors only work with make-rgb-color. The function make-color is an old version of the constructor.

make-rgb-color
Form	(make-rgb-color r g b)
Description	Make and return a color represented by a red, green and blue constituent. This is the primary color constructor of LAML-based software.
Parameters	r	The amount of red - a decimal number between 0 and 255.
	g	The amount of green - a decimal number between 0 and 255.
	b	The amount of blue - a decimal number between 0 and 255.
Returns	A tagged list of color numbers.
Examples	(rgb-color-encoding (make-rgb-color 255 0 0)) => "#ff0000"
	(make-rgb-color 1 2 3) => (rgb-color 1 2 3)
	(red-of-rgb-color (make-rgb-color 1 2 3)) => 1
	(green-of-rgb-color (make-rgb-color 1 2 3)) => 2
	(blue-of-rgb-color (make-rgb-color 1 2 3)) => 3
	(rgb-color? (make-rgb-color 1 2 3)) => #t
See also	Scheme source file	make-rgb-color
	conversion function	rgb-color-encoding

rgb-color?
Form	(rgb-color? x)
Description	Is x a LAML color
Examples	(rgb-color? 1) => #f
	(rgb-color? (make-rgb-color 1 2 3)) => #t
	(rgb-color? (make-color 1 2 3)) => #f
See also	Scheme source file	rgb-color?

red-of-rgb-color
Form	(red-of-rgb-color color)
Description	Return the red constituent of the LAML color.
Parameters	color	A color constructed with make-rgb-color.
Examples	(red-of-rgb-color (make-rgb-color 1 2 3)) => 1
See also	Scheme source file	red-of-rgb-color
	color constructor	make-rgb-color

green-of-rgb-color
Form	(green-of-rgb-color color)
Description	Return the green constituent of the color.
Parameters	color	A color constructed with make-rgb-color.
Examples	(green-of-rgb-color (make-rgb-color 1 2 3)) => 2
See also	Scheme source file	green-of-rgb-color
	color constructor	make-rgb-color

blue-of-rgb-color
Form	(blue-of-rgb-color color)
Description	Return the blue constituent of the color.
Parameters	color	A color constructed with make-rgb-color.
Examples	(blue-of-rgb-color (make-rgb-color 1 2 3)) => 3
See also	Scheme source file	blue-of-rgb-color
	color constructor	make-rgb-color

make-color
Form	(make-color r g b)
Description	Make and return the rgb-list representation of the color with r red, g green, and b blue. This is an old version of the color contructor.
Examples	(rgb-color-encoding (make-color 255 0 0)) => "#ff0000"
	(make-color 1 2 3) => (1 2 3)
	(rgb-color? (make-color 1 2 3)) => #f
See also	Scheme source file	make-color
Note	Deprecated. Use make-rgb-color.

4 Color constants.
To stay backward compatible with a substantial amount of older LAML software, all color constants are bound to the old LAML color representation. Thus, for instance, the value of red is (255 0 0), and not (rgb-color 255 0 0). As an important observation, the primary color encoding function, rgb-color-encoding, accepts the value of the color constants as input (besides a number of other kinds of input).

red
Form	red
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	red

dark-red
Form	dark-red
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	dark-red

green
Form	green
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	green

green1
Form	green1
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	green1

green2
Form	green2
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	green2

blue
Form	blue
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	blue

white
Form	white
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	white

black
Form	black
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	black

yellow
Form	yellow
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	yellow

purple
Form	purple
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	purple

light-blue
Form	light-blue
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	light-blue

blue1
Form	blue1
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	blue1

blue2
Form	blue2
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	blue2

blue3
Form	blue3
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	blue3

orange
Form	orange
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	orange

dark-yellow
Form	dark-yellow
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	dark-yellow

grey1
Form	grey1
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	grey1

grey2
Form	grey2
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	grey2

brown
Form	brown
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	brown

maroon
Form	maroon
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	maroon

grey
Form	grey
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	grey

silver
Form	silver
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	silver

tetal
Form	tetal
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	tetal

aqua
Form	aqua
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	aqua

lime
Form	lime
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	lime

olive
Form	olive
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	olive

navy
Form	navy
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	navy

fuchsia
Form	fuchsia
Description	A color constant. A color is represented as a list of integers of length three (rgb).
See also	Scheme source file	fuchsia

Reference Manual of the Color Library

Kurt Nørmark © normark@cs.aau.dk Department of Computer Science, Aalborg University, Denmark.