vizkit 0.1.3

A rendering-agnostic kit for data visualization
Documentation 
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use super::color::{Color, Cubehelix, Interpolator, color};

#[derive(Clone)]
pub struct CubehelixInterpolator {
    gamma: f32,
    h: Interpolator,
    s: Interpolator,
    l: Interpolator,
}

impl CubehelixInterpolator {
    pub(crate) fn gamma(self, gamma: f32) -> Self {
        Self { gamma, ..self }
    }

    pub(crate) fn interpolate<T>(&self, t: f32) -> T
    where
        Color: Into<T>,
    {
        Color::from(Cubehelix([
            self.h.interpolate(t),
            self.s.interpolate(t),
            self.l.interpolate(t.powf(self.gamma)),
        ]))
        .into()
    }

    pub(crate) fn warm() -> Self {
        let [sh, ss, sl] = [-100., 0.75, 0.35];
        let [eh, es, el] = [80., 1.50, 0.8];
        let h = color(sh, eh);
        let s = color(ss, es);
        let l = color(sl, el);
        Self { gamma: 1., h, s, l }
    }

    pub(crate) fn cold() -> Self {
        let [sh, ss, sl] = [260., 0.75, 0.35];
        let [eh, es, el] = [80., 1.50, 0.8];
        let h = color(sh, eh);
        let s = color(ss, es);
        let l = color(sl, el);
        Self { gamma: 1., h, s, l }
    }
}

impl Default for CubehelixInterpolator {
    fn default() -> Self {
        let [sh, ss, sl] = [300., 0.5, 0.0];
        let [eh, es, el] = [-240., 0.5, 1.0];
        let h = color(sh, eh);
        let s = color(ss, es);
        let l = color(sl, el);
        Self { gamma: 1., h, s, l }
    }
}

#[cfg(test)]
mod tests {
    use super::CubehelixInterpolator;

    #[test]
    fn test_viridis() {
        let step = 100;
        let variants = [
            ("cold", CubehelixInterpolator::cold()),
            ("warm", CubehelixInterpolator::warm()),
        ];

        for (space, interpolator) in variants {
            let colors: Vec<[f32; 3]> = (0..=step)
                .map(|i| interpolator.interpolate(i as f32 / step as f32))
                .collect();
            for color in colors {
                let [r, g, b] = color;
                assert!(
                    (0. ..=1.).contains(&r),
                    "red must be between [0, 1] (variant: {:?})",
                    space
                );
                assert!(
                    (0. ..=1.).contains(&g),
                    "green must be between [0, 1] (variant: {:?})",
                    space
                );
                assert!(
                    (0. ..=1.).contains(&b),
                    "blue must be between [0, 1] (variant: {:?})",
                    space
                );
            }
        }
    }
}