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conversion.sls
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conversion.sls
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;; Copyright 2016 Eduardo Cavazos
;;
;; Licensed under the Apache License, Version 2.0 (the "License");
;; you may not use this file except in compliance with the License.
;; You may obtain a copy of the License at
;;
;; http://www.apache.org/licenses/LICENSE-2.0
;;
;; Unless required by applicable law or agreed to in writing, software
;; distributed under the License is distributed on an "AS IS" BASIS,
;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;; See the License for the specific language governing permissions and
;; limitations under the License.
(library
(agave color conversion)
(export hsva->rgba)
(import (rnrs)
(agave color rgba)
(agave color hsva))
(define (hsva->rgba color)
(let ((hue (inexact (hsva-hue color)))
(saturation (inexact (hsva-saturation color)))
(value (inexact (hsva-value color)))
(alpha (inexact (hsva-alpha color))))
(let ((Hi (mod (floor (/ hue 60.0)) 6.0)))
(let ((f (- (/ hue 60.0) Hi))
(p (* (- 1.0 saturation) value)))
(let ((q (* (- 1.0 (* f saturation)) value))
(t (* (- 1.0 (* (- 1.0 f) saturation)) value)))
(case (exact Hi)
((0) (rgba value t p alpha))
((1) (rgba q value p alpha))
((2) (rgba p value t alpha))
((3) (rgba p q value alpha))
((4) (rgba t p value alpha))
((5) (rgba value p q alpha))))))))
)