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;;; guile-2d
;;; Copyright (C) 2013, 2014 David Thompson <dthompson2@worcester.edu>
;;;
;;; This program is free software: you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Color.
;;
;;; Code:
(define-module (2d color)
#:use-module (gl)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-1)
#:export (<color>
make-color
color?
color-r
color-g
color-b
color-a
rgba
rgb
color*
color+
color-
color-inverse
white
black
red
green
blue
magenta))
(define-record-type <color>
(%make-color r g b a)
color?
(r color-r)
(g color-g)
(b color-b)
(a color-a))
(define (make-color r g b a)
"Return a newly allocated color with the given RGBA channel values.
Each channel is clamped to the range [0, 1]."
(%make-color (clamp 0 1 r)
(clamp 0 1 g)
(clamp 0 1 b)
(clamp 0 1 a)))
(define (color-component color-code offset)
"Return the value of an 8-bit color channel in the range [0,1] for
the integer COLOR-CODE, given an OFFSET in bits."
(let ((mask (ash #xff offset)))
(/ (ash (logand mask color-code)
(- offset))
255.0)))
(define (rgba color-code)
"Translate an RGBA format string COLOR-CODE into a color object.
For example: #xffffffff will return a color with RGBA values 1, 1, 1,
1."
(%make-color (color-component color-code 24)
(color-component color-code 16)
(color-component color-code 8)
(color-component color-code 0)))
(define (rgb color-code)
"Translate an RGB format string COLOR-CODE into a color object.
For example: #xffffff will return a color with RGBA values 1, 1, 1,
1."
(%make-color (color-component color-code 16)
(color-component color-code 8)
(color-component color-code 0)
1))
(define (color* a b)
"Multiply the RGBA channels of colors A and B."
(make-color (* (color-r a)
(color-r b))
(* (color-g a)
(color-g b))
(* (color-b a)
(color-b b))
(* (color-a a)
(color-a b))))
(define (color+ a b)
"Add the RGBA channels of colors A and B."
(make-color (+ (color-r a)
(color-r b))
(+ (color-g a)
(color-g b))
(+ (color-b a)
(color-b b))
(+ (color-a a)
(color-a b))))
(define (color- a b)
"Subtract the RGBA channels of colors A and B."
(make-color (- (color-r a)
(color-r b))
(- (color-g a)
(color-g b))
(- (color-b a)
(color-b b))
(- (color-a a)
(color-a b))))
(define (color-inverse color)
"Create a new color that is the inverse of COLOR. The alpha channel
is left unchanged."
(make-color (- 1 (color-r color))
(- 1 (color-g color))
(- 1 (color-b color))
(color-a color)))
;; Pre-defined colors.
(define white (rgb #xffffff))
(define black (rgb #x000000))
(define red (rgb #xff0000))
(define green (rgb #x00ff00))
(define blue (rgb #x0000ff))
(define magenta (rgb #xff00ff))
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