culors 1.6.0

//! Color-vision-deficiency (CVD) simulation filters.
//!
//! Mirrors culori 4.0.2's `src/deficiency.js`. Three filter factories
//! ([`filter_deficiency_prot`], [`filter_deficiency_deuter`],
//! [`filter_deficiency_trit`]) simulate protanopia, deuteranopia, and
//! tritanopia respectively.
//!
//! The matrices come from Machado, Oliveira, and Fernandes (2009),
//! "A Physiologically-based Model for Simulation of Color Vision
//! Deficiency", IEEE TVCG 15(6), via the precomputed tables published at
//! <https://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html>.
//! Each table has eleven rows for severities 0.0, 0.1, …, 1.0.
//!
//! culori snaps the severity to the nearest tenth (`Math.round(t / 0.1)`)
//! and does not interpolate between tabulated severities. We reproduce
//! that behavior for bit-for-bit parity with culori's output.

use crate::filter::common::to_rgb;
use crate::spaces::Rgb;
use crate::Color;

const PROT: [[f64; 9]; 11] = [
    [1.0, 0.0, -0.0, 0.0, 1.0, 0.0, -0.0, -0.0, 1.0],
    [
        0.856167, 0.182038, -0.038205, 0.029342, 0.955115, 0.015544, -0.00288, -0.001563, 1.004443,
    ],
    [
        0.734766, 0.334872, -0.069637, 0.05184, 0.919198, 0.028963, -0.004928, -0.004209, 1.009137,
    ],
    [
        0.630323, 0.465641, -0.095964, 0.069181, 0.890046, 0.040773, -0.006308, -0.007724, 1.014032,
    ],
    [
        0.539009, 0.579343, -0.118352, 0.082546, 0.866121, 0.051332, -0.007136, -0.011959, 1.019095,
    ],
    [
        0.458064, 0.679578, -0.137642, 0.092785, 0.846313, 0.060902, -0.007494, -0.016807, 1.024301,
    ],
    [
        0.38545, 0.769005, -0.154455, 0.100526, 0.829802, 0.069673, -0.007442, -0.02219, 1.029632,
    ],
    [
        0.319627, 0.849633, -0.169261, 0.106241, 0.815969, 0.07779, -0.007025, -0.028051, 1.035076,
    ],
    [
        0.259411, 0.923008, -0.18242, 0.110296, 0.80434, 0.085364, -0.006276, -0.034346, 1.040622,
    ],
    [
        0.203876, 0.990338, -0.194214, 0.112975, 0.794542, 0.092483, -0.005222, -0.041043, 1.046265,
    ],
    [
        0.152286, 1.052583, -0.204868, 0.114503, 0.786281, 0.099216, -0.003882, -0.048116, 1.051998,
    ],
];

const DEUTER: [[f64; 9]; 11] = [
    [1.0, 0.0, -0.0, 0.0, 1.0, 0.0, -0.0, -0.0, 1.0],
    [
        0.866435, 0.177704, -0.044139, 0.049567, 0.939063, 0.01137, -0.003453, 0.007233, 0.99622,
    ],
    [
        0.760729, 0.319078, -0.079807, 0.090568, 0.889315, 0.020117, -0.006027, 0.013325, 0.992702,
    ],
    [
        0.675425, 0.43385, -0.109275, 0.125303, 0.847755, 0.026942, -0.00795, 0.018572, 0.989378,
    ],
    [
        0.605511, 0.52856, -0.134071, 0.155318, 0.812366, 0.032316, -0.009376, 0.023176, 0.9862,
    ],
    [
        0.547494, 0.607765, -0.155259, 0.181692, 0.781742, 0.036566, -0.01041, 0.027275, 0.983136,
    ],
    [
        0.498864, 0.674741, -0.173604, 0.205199, 0.754872, 0.039929, -0.011131, 0.030969, 0.980162,
    ],
    [
        0.457771, 0.731899, -0.18967, 0.226409, 0.731012, 0.042579, -0.011595, 0.034333, 0.977261,
    ],
    [
        0.422823, 0.781057, -0.203881, 0.245752, 0.709602, 0.044646, -0.011843, 0.037423, 0.974421,
    ],
    [
        0.392952, 0.82361, -0.216562, 0.263559, 0.69021, 0.046232, -0.01191, 0.040281, 0.97163,
    ],
    [
        0.367322, 0.860646, -0.227968, 0.280085, 0.672501, 0.047413, -0.01182, 0.04294, 0.968881,
    ],
];

const TRIT: [[f64; 9]; 11] = [
    [1.0, 0.0, -0.0, 0.0, 1.0, 0.0, -0.0, -0.0, 1.0],
    [
        0.92667, 0.092514, -0.019184, 0.021191, 0.964503, 0.014306, 0.008437, 0.054813, 0.93675,
    ],
    [
        0.89572, 0.13333, -0.02905, 0.029997, 0.9454, 0.024603, 0.013027, 0.104707, 0.882266,
    ],
    [
        0.905871, 0.127791, -0.033662, 0.026856, 0.941251, 0.031893, 0.01341, 0.148296, 0.838294,
    ],
    [
        0.948035, 0.08949, -0.037526, 0.014364, 0.946792, 0.038844, 0.010853, 0.193991, 0.795156,
    ],
    [
        1.017277, 0.027029, -0.044306, -0.006113, 0.958479, 0.047634, 0.006379, 0.248708, 0.744913,
    ],
    [
        1.104996, -0.046633, -0.058363, -0.032137, 0.971635, 0.060503, 0.001336, 0.317922, 0.680742,
    ],
    [
        1.193214, -0.109812, -0.083402, -0.058496, 0.97941, 0.079086, -0.002346, 0.403492, 0.598854,
    ],
    [
        1.257728, -0.139648, -0.118081, -0.078003, 0.975409, 0.102594, -0.003316, 0.501214,
        0.502102,
    ],
    [
        1.278864, -0.125333, -0.153531, -0.084748, 0.957674, 0.127074, -0.000989, 0.601151,
        0.399838,
    ],
    [
        1.255528, -0.076749, -0.178779, -0.078411, 0.930809, 0.147602, 0.004733, 0.691367, 0.3039,
    ],
];

fn pick(lut: &[[f64; 9]; 11], severity: f64) -> [f64; 9] {
    let tt = severity.clamp(0.0, 1.0);
    let i = (tt / 0.1).round() as usize;
    let i = i.min(lut.len() - 1);
    lut[i]
}

fn apply(severity: f64, lut: &[[f64; 9]; 11]) -> impl Fn(&Color) -> Color {
    let m = pick(lut, severity);
    move |color: &Color| {
        let rgb = to_rgb(*color);
        Color::Rgb(Rgb {
            r: m[0] * rgb.r + m[1] * rgb.g + m[2] * rgb.b,
            g: m[3] * rgb.r + m[4] * rgb.g + m[5] * rgb.b,
            b: m[6] * rgb.r + m[7] * rgb.g + m[8] * rgb.b,
            alpha: rgb.alpha,
        })
    }
}

/// Protanopia (red-deficient) simulation. Severity is clamped to `[0, 1]`
/// and then snapped to the nearest tenth, matching culori 4.0.2 (which
/// does no inter-bucket interpolation).
pub fn filter_deficiency_prot(severity: f64) -> impl Fn(&Color) -> Color {
    apply(severity, &PROT)
}

/// Deuteranopia (green-deficient) simulation. Severity is clamped to
/// `[0, 1]` and snapped to the nearest tenth.
pub fn filter_deficiency_deuter(severity: f64) -> impl Fn(&Color) -> Color {
    apply(severity, &DEUTER)
}

/// Tritanopia (blue-deficient) simulation. Severity is clamped to
/// `[0, 1]` and snapped to the nearest tenth.
pub fn filter_deficiency_trit(severity: f64) -> impl Fn(&Color) -> Color {
    apply(severity, &TRIT)
}