cgmath/src/color/hsv.rs

// Copyright 2013 The Lmath Developers. For a full listing of the authors,
// refer to the AUTHORS file at the top-level directory of this distribution.
//
// 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.

use std::num;

use color::{Channel, FloatChannel};
use color::{RGB, ToRGB};

#[path = "../num_macros.rs"]
mod num_macros;

#[deriving(Clone, Eq)]
pub struct HSV<T> { h: T, s: T, v: T }

impl<T> HSV<T> {
    pub fn new(h: T, s: T, v: T) -> HSV<T> {
        HSV { h: h, s: s, v: v }
    }
}

pub trait ToHSV {
    pub fn to_hsv<U:Clone + FloatChannel>(&self) -> HSV<U>;
}

impl<T:Clone + FloatChannel> ToHSV for HSV<T> {
    #[inline]
    pub fn to_hsv<U:Clone + FloatChannel>(&self) -> HSV<U> {
        HSV::new(FloatChannel::from((*self).h.clone()),
                 FloatChannel::from((*self).s.clone()),
                 FloatChannel::from((*self).v.clone()))
    }
}

impl<T:Clone + FloatChannel> ToRGB for HSV<T> {
    pub fn to_rgb<U:Clone + Channel>(&self) -> RGB<U> {
        to_rgb(self.to_hsv::<T>()).to_rgb::<U>()
    }
}

priv fn to_rgb<T:Clone + Float>(color: HSV<T>) -> RGB<T> {
    // Algorithm taken from the Wikipedia article on HSL and HSV:
    // http://en.wikipedia.org/wiki/HSL_and_HSV#From_HSV

    let chr = color.v * color.s;
    let h = color.h / num::cast(60);

    // the 2nd largest component
    let x = chr * (one!(T) - ((h % two!(T)) - one!(T)).abs());

    let mut color_rgb = cond! (
        (h < num::cast(1)) { RGB::new(chr.clone(), x, zero!(T)) }
        (h < num::cast(2)) { RGB::new(x, chr.clone(), zero!(T)) }
        (h < num::cast(3)) { RGB::new(zero!(T), chr.clone(), x) }
        (h < num::cast(4)) { RGB::new(zero!(T), x, chr.clone()) }
        (h < num::cast(5)) { RGB::new(x, zero!(T), chr.clone()) }
        (h < num::cast(6)) { RGB::new(chr.clone(), zero!(T), x) }
        _                  { RGB::new(zero!(T), zero!(T), zero!(T)) }
    );

    // match the value by adding the same amount to each component
    let mn = color.v - chr;

    color_rgb.r = color_rgb.r + mn;
    color_rgb.g = color_rgb.g + mn;
    color_rgb.b = color_rgb.b + mn;

    color_rgb
}