Colors (The Chickadee Game Toolkit)

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5.3.1 Colors

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Merriam-Webster defines color as “a phenomenon of light (such as red, -brown, pink, or gray) or visual perception that enables one to -differentiate otherwise identical objects.” In this essay, I -will… -

Okay, okay. We all know what colors are. Chickadee provides a data -type to represent color and some convenient procedures to work with -them in the (chickadee graphics color) module. Colors are made -up of four components, or channels: red, green, blue, and alpha -(transparency.) Each of these values is expressed as a uniform -floating point value in the range [0, 1]. 0 means that color channel -is unrepresented in the resulting color, whereas 1 means that color -channel is at full intensity. -

Making a color object is easy, and there’s a few ways to do it -depending on what’s most convenient. The first is make-color, -where you specify each channel exactly as described above. This is -fully opaque magenta: -

(make-color 1.0 0.0 1.0 1.0)
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Many people are used to representing colors as 6 or 8 digit -hexadecimal numbers, so Chickadee also allows that. Here’s magenta, -again: -

(rgba #xFF00FFFF)
-(rgb #xFF00FF) ; equivalent to the above
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Procedure: make-color r g b a: Return a new color object with a red value of r, a green value -of g, a blue value of b, and an alpha (transparency) value -of a. All values are clamped to the range [0, 1]. -

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Procedure: rgba color-code: Return a new color object using the values of the first 32 bits of -color-code. Each channel occupies 8 bits. Starting from the -most significant bit, red is first, followed by green, then blue, then -alpha. Color codes are often represented as 6 or 8 digit hexadecimal -numbers in various other programs. -

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Procedure: rgb color-code: Like rgba, but color-code is a 24 bit code with no alpha -channel. -

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Procedure: color? obj: Return #t if obj is a color object. -

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Procedure: color-r color: Return the red channel of color. -

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Procedure: color-g color: Return the green channel of color. -

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Procedure: color-b color: Return the blue channel of color. -

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Procedure: color-a color: Return the alpha channel of color. -

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Procedure: transparency alpha: Return a new color that is white (RGB channels set to 1) with an alpha -channel value of alpha. This can be useful for creating a color -that can be multiplied against another color to make it more -transparent. -

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Procedure: string->color s

Convert the hexadecimal color code in the string s to a color -object. The following string formats are supported: -

(string->color "#FF00FFFF")
-(string->color "FF00FFFF")
-(string->color "#FF00FF")
-(string->color "FF00FF")
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Procedure: color* a b: Multiply the color a with the color or number b and return -a new color with the result. -

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Procedure: color+ a b: Add the color a to the color b and return a new color with -the result. -

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Procedure: color- a b: Subtract the color b from the color a and return a new -color with the result. -

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Procedure: color-inverse color: Invert the red, green, and blue channels of color and return a -new color with the result. -

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Procedure: color-lerp start end alpha: Linearly interpolate the colors start and end using the -factor alpha, a number in the range [0, 1]. -

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5.3.1.1 Stock Colors

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For convenience, Chickadee comes with some basic colors predefined: -

Variable: white

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Variable: black

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Variable: red

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Variable: green

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Variable: blue

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Variable: yellow

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Variable: magenta

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Variable: cyan

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For fun, there are also predefined colors for the classic -Tango color palette. -

Variable: tango-light-butter

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Variable: tango-butter

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Variable: tango-dark-butter

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Variable: tango-light-orange

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Variable: tango-orange

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Variable: tango-dark-orange

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Variable: tango-light-chocolate

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Variable: tango-chocolate

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Variable: tango-dark-chocolate

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Variable: tango-light-chameleon

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Variable: tango-chameleon

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Variable: tango-dark-chameleon

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Variable: tango-light-sky-blue

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Variable: tango-sky-blue

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Variable: tango-dark-sky-blue

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Variable: tango-light-plum

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Variable: tango-plum

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Variable: tango-dark-plum

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Variable: tango-light-scarlet-red

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Variable: tango-scarlet-red

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Variable: tango-dark-scarlet-red

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Variable: tango-aluminium-1

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Variable: tango-aluminium-2

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Variable: tango-aluminium-3

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Variable: tango-aluminium-4

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Variable: tango-aluminium-5

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Variable: tango-aluminium-6

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