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Diffstat (limited to '2d')
-rw-r--r--2d/helpers.scm16
1 files changed, 15 insertions, 1 deletions
diff --git a/2d/helpers.scm b/2d/helpers.scm
index 153b4b5..c919006 100644
--- a/2d/helpers.scm
+++ b/2d/helpers.scm
@@ -23,8 +23,10 @@
(define-module (2d helpers)
#:use-module (srfi srfi-1)
+ #:use-module (rnrs arithmetic bitwise)
#:export (any-equal?
- logand?))
+ logand?
+ rgba->gl-color))
(define (any-equal? elem . args)
"Returns true if elem equals any of the arguments and returns false
@@ -35,3 +37,15 @@ otherwise."
"Returns true if the result of a bitwise AND of the integer
arguments is non-zero and returns false otherwise."
(not (zero? (apply logand args))))
+
+(define (rgba->gl-color color)
+ "Converts an integer color code into OpenGL compatible color
+values. Returns a list of four floating point numbers in range [0,1]."
+ (define (component offset)
+ (let ((mask (bitwise-arithmetic-shift-left #xff offset)))
+ (/ (bitwise-arithmetic-shift-right (logand mask color) offset) 255.0)))
+
+ (list (component 24)
+ (component 16)
+ (component 8)
+ (component 0)))