use super::{f32, Lab};
pub struct DE2000;
impl DE2000 {
pub fn new(color_1: Lab, color_2: Lab) -> f32 {
let ksub_l = 1.0;
let ksub_c = 1.0;
let ksub_h = 1.0;
let delta_l_prime = color_2.l - color_1.l;
let l_bar = (color_1.l + color_2.l) / 2.0;
let c1 = (color_1.a.powi(2) + color_1.b.powi(2)).sqrt();
let c2 = (color_2.a.powi(2) + color_2.b.powi(2)).sqrt();
let c_bar = (c1 + c2) / 2.0;
let a_prime_1 =
color_1.a + (color_1.a / 2.0) * (1.0 - (c_bar.powi(7) / (c_bar.powi(7) + 25f32.powi(7))).sqrt());
let a_prime_2 =
color_2.a + (color_2.a / 2.0) * (1.0 - (c_bar.powi(7) / (c_bar.powi(7) + 25f32.powi(7))).sqrt());
let c_prime_1 = (a_prime_1.powi(2) + color_1.b.powi(2)).sqrt();
let c_prime_2 = (a_prime_2.powi(2) + color_2.b.powi(2)).sqrt();
let c_bar_prime = (c_prime_1 + c_prime_2) / 2.0;
let delta_c_prime = c_prime_2 - c_prime_1;
let s_sub_l = 1.0 +
((0.015 * (l_bar - 50.0).powi(2)) / (20.0 + (l_bar - 50.0).powi(2)).sqrt());
let s_sub_c = 1.0 + 0.045 * c_bar_prime;
let h_prime_1 = get_h_prime_fn(color_1.b, a_prime_1);
let h_prime_2 = get_h_prime_fn(color_2.b, a_prime_2);
let delta_h_prime = get_delta_h_prime(c1, c2, h_prime_1, h_prime_2);
let delta_upcase_h_prime = 2.0 * (c_prime_1 * c_prime_2).sqrt() *
(degrees_to_radians(delta_h_prime) / 2.0).sin();
let upcase_h_bar_prime = get_upcase_h_bar_prime(h_prime_1, h_prime_2);
let upcase_t = get_upcase_t(upcase_h_bar_prime);
let s_sub_upcase_h = 1.0 + 0.015 * c_bar_prime * upcase_t;
let r_sub_t = get_r_sub_t(c_bar_prime, upcase_h_bar_prime);
let lightness: f32 = delta_l_prime / (ksub_l * s_sub_l);
let chroma: f32 = delta_c_prime / (ksub_c * s_sub_c);
let hue: f32 = delta_upcase_h_prime / (ksub_h * s_sub_upcase_h);
(lightness.powi(2) + chroma.powi(2) + hue.powi(2) + r_sub_t * chroma * hue).sqrt()
}
pub fn from_rgb(color_1: &[u8; 3], color_2: &[u8; 3]) -> f32 {
let lab_1 = Lab::from_rgb(color_1);
let lab_2 = Lab::from_rgb(color_2);
DE2000::new(lab_1, lab_2)
}
}
fn get_h_prime_fn(x: f32, y: f32) -> f32 {
let mut hue_angle;
if x == 0.0 && y == 0.0 {
return 0.0;
}
hue_angle = radians_to_degrees(x.atan2(y));
if hue_angle < 0.0 {
hue_angle += 360.0;
}
hue_angle
}
fn get_delta_h_prime(c1: f32, c2: f32, h_prime_1: f32, h_prime_2: f32) -> f32 {
if 0.0 == c1 || 0.0 == c2 {
return 0.0;
}
if (h_prime_1 - h_prime_2).abs() <= 180.0 {
return h_prime_2 - h_prime_1;
}
if h_prime_2 <= h_prime_1 {
h_prime_2 - h_prime_1 + 360.0
} else {
h_prime_2 - h_prime_1 - 360.0
}
}
fn get_upcase_h_bar_prime(h_prime_1: f32, h_prime_2: f32) -> f32 {
if (h_prime_1 - h_prime_2).abs() > 180.0 {
return (h_prime_1 + h_prime_2 + 360.0) / 2.0;
}
(h_prime_1 + h_prime_2) / 2.0
}
fn get_upcase_t(upcase_h_bar_prime: f32) -> f32 {
1.0 - 0.17 * (degrees_to_radians(upcase_h_bar_prime - 30.0)).cos() +
0.24 * (degrees_to_radians(2.0 * upcase_h_bar_prime)).cos() +
0.32 * (degrees_to_radians(3.0 * upcase_h_bar_prime + 6.0)).cos() -
0.20 * (degrees_to_radians(4.0 * upcase_h_bar_prime - 63.0)).cos()
}
fn get_r_sub_t(c_bar_prime: f32, upcase_h_bar_prime: f32) -> f32 {
-2.0 * (c_bar_prime.powi(7) / (c_bar_prime.powi(7) + 25f32.powi(7))).sqrt() *
(degrees_to_radians(60.0 * (-(((upcase_h_bar_prime - 275.0) / 25.0).powi(2))).exp())).sin()
}
fn radians_to_degrees(radians: f32) -> f32 {
radians * (180.0 / f32::consts::PI)
}
fn degrees_to_radians(degrees: f32) -> f32 {
degrees * (f32::consts::PI / 180.0)
}
#[cfg(test)]
mod tests {
use super::{DE2000, Lab};
fn round(val: f32) -> f32 {
let rounded = val * 10000 as f32;
rounded.round() / 10000 as f32
}
fn assert_delta_e(expected: f32, lab1: &[f32; 3], lab2: &[f32; 3]) {
let color_1 = Lab {
l: lab1[0],
a: lab1[1],
b: lab1[2],
};
let color_2 = Lab {
l: lab2[0],
a: lab2[1],
b: lab2[2],
};
assert_eq!(round(DE2000::new(color_1, color_2)), expected);
}
#[test]
fn tests() {
assert_delta_e(0.0, &[0.0, 0.0, 0.0], &[0.0, 0.0, 0.0]);
assert_delta_e(0.0, &[99.5, 0.005, -0.010], &[99.5, 0.005, -0.010]);
assert_delta_e(100.0, &[100.0, 0.005, -0.010], &[0.0, 0.0, 0.0]);
assert_delta_e(2.0425, &[50.0000, 2.6772, -79.7751], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(2.8615, &[50.0000, 3.1571, -77.2803], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(3.4412, &[50.0000, 2.8361, -74.0200], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(1.0000, &[50.0000, -1.3802, -84.2814], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(1.0000, &[50.0000, -1.1848, -84.8006], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(1.0000, &[50.0000, -0.9009, -85.5211], &[50.0000, 0.0000, -82.7485]);
assert_delta_e(2.3669, &[50.0000, 0.0000, 0.0000], &[50.0000, -1.0000, 2.0000]);
assert_delta_e(2.3669, &[50.0000, -1.0000, 2.0000], &[50.0000, 0.0000, 0.0000]);
assert_delta_e(7.1792, &[50.0000, 2.4900, -0.0010], &[50.0000, -2.4900, 0.0009]);
assert_delta_e(7.1792, &[50.0000, 2.4900, -0.0010], &[50.0000, -2.4900, 0.0010]);
assert_delta_e(7.2195, &[50.0000, 2.4900, -0.0010], &[50.0000, -2.4900, 0.0011]);
assert_delta_e(7.2195, &[50.0000, 2.4900, -0.0010], &[50.0000, -2.4900, 0.0012]);
assert_delta_e(4.8045, &[50.0000, -0.0010, 2.4900], &[50.0000, 0.0009, -2.4900]);
assert_delta_e(4.7461, &[50.0000, -0.0010, 2.4900], &[50.0000, 0.0011, -2.4900]);
assert_delta_e(4.3065, &[50.0000, 2.5000, 0.0000], &[50.0000, 0.0000, -2.5000]);
assert_delta_e(27.1492, &[50.0000, 2.5000, 0.0000], &[73.0000, 25.0000, -18.0000]);
assert_delta_e(22.8977, &[50.0000, 2.5000, 0.0000], &[61.0000, -5.0000, 29.0000]);
assert_delta_e(31.9030, &[50.0000, 2.5000, 0.0000], &[56.0000, -27.0000, -3.0000]);
assert_delta_e(19.4535, &[50.0000, 2.5000, 0.0000], &[58.0000, 24.0000, 15.0000]);
assert_delta_e(1.0000, &[50.0000, 2.5000, 0.0000], &[50.0000, 3.1736, 0.5854]);
assert_delta_e(1.0000, &[50.0000, 2.5000, 0.0000], &[50.0000, 3.2972, 0.0000]);
assert_delta_e(1.0000, &[50.0000, 2.5000, 0.0000], &[50.0000, 1.8634, 0.5757]);
assert_delta_e(1.0000, &[50.0000, 2.5000, 0.0000], &[50.0000, 3.2592, 0.3350]);
assert_delta_e(1.2644, &[60.2574, -34.0099, 36.2677], &[60.4626, -34.1751, 39.4387]);
assert_delta_e(1.2630, &[63.0109, -31.0961, -5.8663], &[62.8187, -29.7946, -4.0864]);
assert_delta_e(1.8731, &[61.2901, 3.7196, -5.3901], &[61.4292, 2.2480, -4.9620]);
assert_delta_e(1.8645, &[35.0831, -44.1164, 3.7933], &[35.0232, -40.0716, 1.5901]);
assert_delta_e(2.0373, &[22.7233, 20.0904, -46.6940], &[23.0331, 14.9730, -42.5619]);
assert_delta_e(1.4146, &[36.4612, 47.8580, 18.3852], &[36.2715, 50.5065, 21.2231]);
assert_delta_e(1.4441, &[90.8027, -2.0831, 1.4410], &[91.1528, -1.6435, 0.0447]);
assert_delta_e(1.5381, &[90.9257, -0.5406, -0.9208], &[88.6381, -0.8985, -0.7239]);
assert_delta_e(0.6377, &[6.7747, -0.2908, -2.4247], &[5.8714, -0.0985, -2.2286]);
assert_delta_e(0.9082, &[2.0776, 0.0795, -1.1350], &[0.9033, -0.0636, -0.5514]);
}
}