6 RRLL: Color Support

8.10

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6 RRLL: Color Support

Dominik Pantůček <dominik.pantucek@trustica.cz>

Racket Rogue-Like Library: Color Support

Various utilitis for color manipulation, blending and lighting.

6.1 Core Color Functions

(require rrll/color/core)

package: rrll-color

Requiring this module raises error if the system word size is less than 64 bits.

value
alpha-max : fixnum? = #xff

Defines the maximum alpha channel value for 32-bit ARGB color representation.

value
alpha-mask : fixnum? = #xff000000

Bit mask of the alpha channel part or 32-bit ARGB color representation.

procedure
(split-rgb color) →
fixnum? fixnum? fixnum?
color : fixnum?

Splits given 24-bit RGB value into its 8-bit components.

procedure
(split-argb color) →
fixnum? fixnum? fixnum? fixnum?
color : fixnum?

Splits given 32-bit ARGB value into its 8-bit components.

procedure
(make-rgb r g b) → fixnum?
  r : fixnum?
  g : fixnum?
  b : fixnum?

Creates a 24-bit RGB color from 8-bit components.

procedure
(make-argb a r g b) → fixnum?
  a : fixnum?
  r : fixnum?
  g : fixnum?
  b : fixnum?

Creates a 32-bit ARGB color from 8-bit components.

procedure
(extract-argb-alpha argb) → fixnum?
argb : fixnum?

Extracts only alpha-channel value from given 32-bit ARGB color.

procedure
(set-argb-alpha argb alpha) → fixnum?
argb : fixnum?
alpha : fixnum?

Modifies given ARGB value and returns a new one with the alpha channel replaced by the explicit value given.

procedure
(rgb-distance^2 c1 c2) → fixnum?
c1 : fixnum?
c2 : fixnum?

Computes the square of euclidean distance in RGB space of the two colors given.

d=(r_1-r_2)^2+(g_1-g_2)^2+(b_1-b_2)^2

procedure
(is-argb? -rgb) → boolean?
-rgb : fixnum?

Returns #t if the given -rgb value has non-zero alpha channel.

6.2 Color Blending

(require rrll/color/blending)

package: rrll-color

procedure
(rgb-average color ...) → fixnum?
color : fixnum?

Averages given RGB values.

procedure
(rgb-average2 c0 c1) → fixnum?
c0 : fixnum?
c1 : fixnum?

Optimized implementation that averages two RGB values.

procedure
(rgb-average4 c0 c1 c2 c3) → fixnum?
  c0 : fixnum?
  c1 : fixnum?
  c2 : fixnum?
  c3 : fixnum?

Optimized implementation that averages four RGB values.

procedure
(argb-average color ...) → fixnum?
color : fixnum?

Averages given ARGB values.

procedure
(argb-average2 c0 c1) → fixnum?
c0 : fixnum?
c1 : fixnum?

Optimized implementation that averages two ARGB values.

procedure
(argb-average4 c0 c1 c2 c3) → fixnum?
  c0 : fixnum?
  c1 : fixnum?
  c2 : fixnum?
  c3 : fixnum?

Optimized implementation that averages four ARGB values.

procedure
(alpha-blend-alpha a1 a2) → fixnum?
a1 : fixnum?
a2 : fixnum?

Blends alpha2 alpha value over alpha1 value using:

\alpha=\alpha_1\cdot\alpha_2

\alpha_1,\alpha_2\in\langle 0;255\rangle \equiv \langle 0.0;1.0\rangle

procedure
(rgb-blend-argb rgb argb) → fixnum?
rgb : fixnum?
argb : fixnum?

Blends argb over rgb based on the alpha channel value.

procedure
(rgb-blend-rgb+alpha rgb0 rgb1 alpha) → fixnum?
  rgb0 : fixnum?
  rgb1 : fixnum?
  alpha : fixnum?

Blends rgb1 over rgb0 based on the alpha value.

\alpha\in\langle 0;255\rangle\equiv\langle 0.0;1.0\rangle

procedure
(rgb-blend-argb+alpha rgb argb alpha) → fixnum?
  rgb : fixnum?
  argb : fixnum?
  alpha : fixnum?

Blends argb over rgb based on the combined alpha channel and given alpha value.

\alpha\in\langle 0;255\rangle\equiv\langle 0.0;1.0\rangle

Uses alpha-blend-alpha to merge argb’s alpha channel with the alpha value.

procedure
(rgb-linear c0 c1 f) → fixnum?
  c0 : fixnum?
  c1 : fixnum?
  f : fixnum?

Linearly interpolates two RGB colors using given f factor.

f\in\langle 0;256\rangle\equiv\langle 0.0;1.0\rangle

procedure
(argb-linear c0 c1 f) → fixnum?
  c0 : fixnum?
  c1 : fixnum?
  f : fixnum?

Linearly interpolates two ARGB colors using given f factor.

f\in\langle 0;256\rangle\equiv\langle 0.0;1.0\rangle

procedure
(rgb-bilinear r0c0 r0c1 r1c0 r1c1 u v) → fixnum?
  r0c0 : fixnum?
  r0c1 : fixnum?
  r1c0 : fixnum?
  r1c1 : fixnum?
  u : fixnum?
  v : fixnum?

Performs bilinear interpolation between four RGB colors.

u,v\in\langle 0;256\rangle\equiv\langle 0.0;1.0\rangle

procedure
(argb-bilinear r0c0 r0c1 r1c0 r1c1 u v) → fixnum?
  r0c0 : fixnum?
  r0c1 : fixnum?
  r1c0 : fixnum?
  r1c1 : fixnum?
  u : fixnum?
  v : fixnum?

Performs bilinear interpolation between four ARGB colors.

u,v\in\langle 0;256\rangle\equiv\langle 0.0;1.0\rangle

6.3 Color Names

(require rrll/color/names)

package: rrll-color

The following 16 fixnum? constants are defined:

BLACK BLUE GREEN CYAN RED MAGENTA BROWN LIGHTGRAY DARKGRAY LIGHTBLUE LIGHTGREEN LIGHTCYAN LIGHTRED LIGHTMAGENTA YELLOW WHITE

value
CGA-COLORS : (vectorof fixnum?)

Contains the ordered vector of 16 aforementioned CGA colors.

6.4 Flonum Colors

(require rrll/color/flcolor)

package: rrll-color

This module provides flonum?-based RGB and ARGB processing used when color interpolation is required.

procedure
(make-flrgb r g b) → flvector?
  r : flonum?
  g : flonum?
  b : flonum?

Creates new RGB triplet. The result is (flvector b g r) to keep the in-memory ordering the same as with byte-channel RGB.

procedure
(make-flargb a r g b) → flvector?
  a : flonum?
  r : flonum?
  g : flonum?
  b : flonum?

Creates new RGB triplet. The result is (flvector b g r a) to keep the in-memory ordering the same as with byte-channel ARGB.

procedure
(split-flrgb fc) →
flonum? flonum? flonum?
fc : flvector?

Returns the red, green and blue channels as separate values. See make-flrgb for the in-memory data ordering.

procedure
(split-flargb fc) →
flonum? flonum? flonum? flonum?
fc : flvector?

Returns the alpha, red, green and blue channels as separate values. See make-flargb for the in-memory data ordering.

procedure
(rgb->flrgb c) → flvector?
c : fixnum?

Convers given RGB color (see make-rgb) to flvector? RGB represenation (see make-flrgb).

procedure
(flrgb->rgb fc) → fixnum?
fc : flvector?

Converts given flonum? RGB color to single-fixnum? color. See make-flrgb for the former and make-rgb for the latter.

procedure
(argb->flargb c) → flvector?
c : fixnum?

Convers given ARGB color (see make-argb) to flvector? ARGB represenation (see make-flargb).

procedure
(flargb->argb fc) → fixnum?
fc : flvector?

Converts given flonum? ARGB color to single-fixnum? color. See make-flargb for the former and make-argb for the latter.

procedure
(flrgb-add fc1 fc2) → flvector?
fc1 : flvector?
fc2 : flvector?

Adds two flonum? RGB triplets together. No clamping is performed.

procedure
(flargb-add fc1 fc2) → flvector?
fc1 : flvector?
fc2 : flvector?

Adds two flonum? ARGB quadruplets together. No clamping is performed.

procedure
(flrgb-div fc n) → flvector?
fc : flvector?
n : flonum?

Divides all components of a flonum? RGB color by given number.

procedure
(flargb-div fc n) → flvector?
fc : flvector?
n : flonum?

Divides all components of a flonum? ARGB color by given number.

procedure
(flrgb-mul fc n) → flvector?
fc : flvector?
n : flonum?

Multiplies all components of a flonum? RGB color by given number.

procedure
(flargb-mul fc n) → flvector?
fc : flvector?
n : flonum?

Multiplies all components of a flonum? ARGB color by given number.

6.5 Color Lighting

(require rrll/color/lighting)

package: rrll-color

This module provides reference implementaiton of colored lighting routines to be used by the renderer mostly for Goraud shading.

procedure
(make-light r g b) → flvector?
  r : flonum?
  g : flonum?
  b : flonum?

Creates a colored light data structure of three fload numbers in single flvector?.

procedure
(light-rgb rgb l) → fixnum?
rgb : fixnum?
l : flvector?

Applies colored light to given color value and returns the lit color.

Each component is adjusted according to:

c=c_0\cdot l

The result is fxclamped in \langle 0;255\rangle.

procedure
(light-argb argb l) → fixnum?
argb : fixnum?
l : flvector?

Applies colored light to given color value and returns the lit color like light-rgb. The alpha component of the color is kept unchanged.

procedure
(light-add l1 l2) → flvector?
l1 : flvector?
l2 : flvector?

An alias for flrgb-add.

6.6 Random Colors

(require rrll/color/random)

package: rrll-color

Helper module for random RGB and ARGB colors where needed.

procedure
(random-rgb) → fixnum?

Generates valid random RGB color.

procedure
(random-argb) → fixnum?

Generates valid random ARGB quadruplet.

6.7 Color Interpolation

(require rrll/color/interpolate)

package: rrll-color

This module implements a special format with more bits per channel to allow simple iteration over (possibly multi-dimensional) field of color values.

procedure
(rgb+add rgb+1 rgb+2) → fixnum?
rgb+1 : fixnum?
rgb+2 : fixnum?

Adds two RGB+ values maintaining the bit format.

procedure
(make-rgb+ r g b) → fixnum?
  r : flonum?
  g : flonum?
  b : flonum?

Returns RGB+ representation of given RGB triplet.

procedure
(rgb+>rgb rgb+) → fixnum?
rgb+ : fixnum?

Converts to standard RGB representation.

procedure
(argb+add argb+1 argb+2) → fixnum?
argb+1 : fixnum?
argb+2 : fixnum?

Adds two ARGB+ values maintaining the bit format.

procedure
(make-argb+ a r g b) → fixnum?
  a : flonum?
  r : flonum?
  g : flonum?
  b : flonum?

Returns ARGB+ representation of given ARGB quadruplet.

procedure
(argb+>argb argb+) → fixnum?
argb+ : fixnum?

Converts to standard ARGB representation.

6.8 Fixed-Point Color Light

(require rrll/color/fxlight)

package: rrll-color

procedure
(fxlight-rgb rgbc rgbl) → fixnum?
rgbc : fixnum?
rgbl : fixnum?

Lights given rgbc color using the rgbl light. The light components are interpreted as follows:

0 is no light at all
127 is 100% of the original color component intensity
255 is almost 200% (256 would be the actual 200% intensity)

These values were chosen purely for performance reasons.

procedure
(fxlight-argb argbc rgbl) → fixnum?
argbc : fixnum?
rgbl : fixnum?

Lights the argbc color using rgbl light, preserving the alpha channel of the source.

contents ← prev up next →

1	RRLL: Actor Basic 2.0
2	RRLL: ANSI Buffers
3	RRLL: Abuf Canvas
4	RRLL: Canvas
5	RRLL: Rendering Canvas
6	RRLL: Color Support
7	RRLL: Single-Channel Flomaps
8	RRLL: Futures
9	RRLL: Functional Grids
10	RRLL: Helpers
11	RRLL: Math
12	RRLL: Mutable Future Queue
13	RRLL: Rasterizer
14	RRLL: Renderer
15	RRLL: Terminal I/ O
16	RRLL: Ticker
17	RRLL: Unsafe

6.1	Core Color Functions
6.2	Color Blending
6.3	Color Names
6.4	Flonum Colors
6.5	Color Lighting
6.6	Random Colors
6.7	Color Interpolation
6.8	Fixed-Point Color Light