Color Hollow ¶

Color Hollow. A color management module.

Procedures ¶

rgb-cc->color

rgba-cc->color

string->color

color-blend

Description ¶

Welcome to the G-Golf Color Hollow, partially inspired by the Chickadee’s color module and the Colorways python library.

In G-Golf, a color is a list of 4 floats in the [0 1] range, each representing the value of the RED (r), GREEN (g), BLUE (b) and ALPHA (a) channels, in that order. For example, an opaque red color instance would be ’(1.0 0.0 0.0 1.0).

G-Golf offers several ways to obtain the list representation of a color, in addition to manually listing the values as showned above:

1. processing its hexadecimal representation

   (rgb-cc->color #x73d216)      ;; cc = color code
   ⇒ (0.45 0.82 0.09 1.0)
   
   (rgba-cc->color #x73d216aa)
   ⇒ (0.45 0.82 0.09 0.67)
   

   In the above examples, #x73d216 is the RGB hexadecimal representation of the (opaque) color, and #x73d216aa is the RGBA hexadecimal representation of the same color with an alpha channel value of 0.67 ²⁶.

2. calling string->color

   (string->color "deepskyblue")
   ⇒ (0 3/4 1 1.0)
   
   (string->color "#aabbccdd")
   ⇒ (0.67 0.73 0.8 0.87)
   

3. refering predefined color symbols

   +blue+
   ⇒ (0 0 1 1.0)
   
   +blanched-almond+
   ⇒ (1 23/25 4/5 1.0)
   

^_ Predefined Color Symbols

G-Golf pre-defines color symbols that come from the following color dictionaries:

• Pango and Gdk (known) colors - As defined here.

  The file mentioned in the above link is maintained by the GNOME team - composed of (sometimes modified) X11 (rgb.txt) and CSS colors - it is used by both the Pango and the Gdk libraries.

• Tango color palette - As described here.
• DawnBringer 32 color palette - As defined here, names taken from here.

Pre-defined color symbols available in G-Golf are defined by taking their corresponding color dictionary entry name, substitute any #\Space by #\-, call g-name->name (which calls g-studly-caps-expand), then pre and postfix the returned symbol name using +. For example:

  +antique-white+
  ⇒ (49/50 23/25 21/25 1.0)

  +tango-chocolate-dark+
  ⇒ (14/25 7/20 1/100 1.0)

  +db32-elf-green+
  ⇒ (11/50 29/50 43/100 1.0)

  +rebeccapurple+
  ⇒ (2/5 1/5 3/5 1.0)

^_ Color Blending

Color blending formulas are mostly taken from here. This is a wip (Work In Progress), as G-Golf currently only provides a few of the numerous color blending modes, to be enhanced in the future.

Unless otherwise specified, color blending procedures (deliberately) apply their formula to the R G B channels (only), and return a (newly allocated) color for which the A (alpha) channel is the base A channel value.

Procedures ¶

Procedure: rgb-cc->color cc ¶

Returns a color, composed of the Red, Green, Blue values for cc (color code), in the [0,1] range, and 1.0 for the Alpha channel.

  (rgb-cc->color #x73d216)
  ⇒ (0.45 0.82 0.09 1.0)

Procedure: rgba-cc->color cc ¶

Returns a color, composed of the Red, Green, Blue, Alpha values for cc (color code), in the [0,1] range.

  (rgba-cc->color #x73d216aa)
  ⇒ (0.45 0.82 0.09 0.67)

Procedure: string->color str ¶

Returns the color, for str.

A valid str value is either an existing G-Golf color dictionary name entry, or an hexadecimal color string. Accepted hexadecimal color string formats are: ‘#rrggbb’, ‘rrggbb’, ‘#rrggbbaa’ and ‘rrggbbaa’.

  (string->color "#73d216aa")
  ⇒ (0.45 0.82 0.09 0.67)

Procedure: color-blend mode base [blend #f] ¶

Returns a (newly allocated) color.

Unless otherwise specified, color blending procedures (deliberately) apply their formula to the R G B channels (only), and return a (newly allocated) color for which the A (alpha) channel is the base A channel value.

The base argument must be a color. The blend argument can either be a color or a float in the [0 1] range (in which case it can also be omited, so as to compute the result of the alternative color blending formula using the default value), for example:

  (color-blend 'darken +red+)
  ⇒ (0.8 0.0 0.0 1.0)

  (color-blend 'darken +red+ 0.3)
  ⇒ (0.7 0.0 0.0 1.0)

  (color-blend 'darken +alice-blue+ +dark-blue+)
  ⇒ (0 0 11/20 1.0)

The mode argument is a symbol. Currently accepted blending mode and alternative color blending formulas are, applied to each of the R G B channel values:

darken

darken base
⇒ (max 0.0 (- chan (* chan 0.2)))

darken base float
⇒ (max 0.0 (- chan (* chan float)))

darken base blend
⇒ (min base-chan blend-chan)

lighten

lighten base
⇒ (min 1.0 (+ chan (* chan 0.2)))

lighten base float
⇒ (min 1.0 (+ chan (* chan float)))

lighten base blend
⇒ (min base-chan blend-chan)