rust-hsluv 0.1.4

use std::f64::consts::PI;
use std::cmp::Ordering;
use std::str;

const M: [[f64;3];3] = [
	[3.240969941904521, -1.537383177570093, -0.498610760293],
	[-0.96924363628087, 1.87596750150772, 0.041555057407175],
	[0.055630079696993, -0.20397695888897, 1.056971514242878],
];

const M_INV: [[f64;3];3] = [

	[0.41239079926595, 0.35758433938387, 0.18048078840183],
	[0.21263900587151, 0.71516867876775, 0.072192315360733],
	[0.019330818715591, 0.11919477979462, 0.95053215224966],
];

const REF_Y : f64   = 1.0;
const REF_U : f64   = 0.19783000664283;
const REF_V : f64   = 0.46831999493879;
// CIE LUV constants
const KAPPA : f64   = 903.2962962;
const EPSILON : f64 = 0.0088564516;

/// Convert HSLUV to HEX
pub fn hsluv_to_hex(hsl: (f64, f64, f64)) -> String {
	rgb_to_hex(
		hsluv_to_rgb(hsl)
	)
}

/// Convert HPLUV to HEX
pub fn hpluv_to_hex(hsl: (f64, f64, f64)) -> String {
	rgb_to_hex(
		hpluv_to_rgb(hsl)
	)
}

/// Convert HEX to HSLUV
pub fn hex_to_hsluv(hex: &str) -> (f64, f64, f64) {
	rgb_to_hsluv(
		hex_to_rgb(hex)
	)
}

/// Convert HEX to HPLUV
pub fn hex_to_hpluv(hex: &str) -> (f64, f64, f64) {
	rgb_to_hpluv(
		hex_to_rgb(hex)
	)
}

/// Convert HSLUV to LCH
pub fn hsluv_to_lch(hsl: (f64, f64, f64)) ->(f64, f64, f64) {
	let (h, s, l) = hsl;
	match l {
		l if l > 99.9999999 => (100.0, 0.0, h),
		l if l < 0.00000001 => (0.0, 0.0, h),
		_ => {
			let mx = max_chroma_for(l, h);
			let c = mx/100.0 * s;
			(l, c, h)
		}
	}
}

/// Convert HPLUV to LCH
pub fn hpluv_to_lch(hpl: (f64, f64, f64) ) -> (f64, f64, f64) {
	let (h, p, l) = hpl;
	match l {
		l if l > 99.9999999 => (100.0, 0.0, h),
		l if l < 0.00000001 => (0.0, 0.0, h),
		_ => {
			let mx = max_safe_chroma_for(l);
			let c = mx/100.0 * p;
			(l, c, h)
		}
	}
}

/// Convert LCH to LUV
pub fn lch_to_luv(lch: (f64, f64, f64)) -> (f64, f64, f64) {
	let (l, c, h) = lch;
	let hrad = degrees_to_radians(h);
	let u = hrad.cos() * c;
	let v = hrad.sin() * c;

	(l, u, v)
}

/// Convert LCH to HSLUV
pub fn lch_to_hsluv(lch: (f64, f64, f64)) -> (f64, f64, f64) {
	let (l, c, h) = lch;
	match l {
		l if l > 99.9999999 => (h, 0.0, 100.0),
		l if l < 0.00000001 => (h, 0.0, 0.0),
		_ => {
			let mx = max_chroma_for(l, h);
			let s = c / mx * 100.0;
			(h, s, l)
		}
	}
}

/// Convert LCH to HPLUV
pub fn lch_to_hpluv(lch: (f64, f64, f64)) -> (f64, f64, f64) {
	let (l, c, h) = lch;
	match l {
		l if l > 99.9999999 => (h, 0.0, 100.0),
		l if l < 0.00000001 => (h, 0.0, 0.0),
		_ => {
			let mx = max_safe_chroma_for(l);
			let s = c / mx * 100.0;
			(h, s, l)
		}
	}
}

/// Convert LCH to RGB
pub fn lch_to_rgb(lch: (f64, f64, f64)) -> (f64, f64, f64) {
	xyz_to_rgb(
		luv_to_xyz(
			lch_to_luv(lch)
		)
	)
}

/// Convert HSLUV to RGB
pub fn hsluv_to_rgb(hsl: (f64, f64, f64)) -> (f64, f64, f64) {
	xyz_to_rgb(
		luv_to_xyz(
			lch_to_luv(
				hsluv_to_lch(hsl)
			)
		)
	)
}

/// Convert HPLUV to RGB
pub fn hpluv_to_rgb(hsl: (f64, f64, f64)) -> (f64, f64, f64) {
	lch_to_rgb(
		hpluv_to_lch(hsl)
	)
}

/// Convert XYZ to RGB
pub fn xyz_to_rgb(xyz: (f64, f64, f64)) -> (f64, f64, f64) {
	let xyz_vec = vec![xyz.0, xyz.1, xyz.2];
	let abc: Vec<f64> = M.iter().map(|i| from_linear(dot_product(&i.to_vec(), &xyz_vec))).collect();
	(abc[0], abc[1], abc[2])
}

/// Convert LUV to XYZ
pub fn luv_to_xyz(luv: (f64, f64, f64)) -> (f64, f64, f64) {
	let (l, u, v) = luv;

	if l == 0.0 {
		return (0.0, 0.0, 0.0);
	}

	let var_y = f_inv(l);
	let var_u = u / (13.0 * l) + REF_U;
	let var_v = v / (13.0 * l) + REF_V;

	let y = var_y * REF_Y;
	let x = 0.0 - (9.0 * y * var_u) / ((var_u - 4.0) * var_v - var_u * var_v);
	let z = (9.0 * y - (15.0 * var_v * y) - (var_v * x)) / (3.0 * var_v);

	(x, y, z)
}

/// Convert XYZ to LUV
pub fn xyz_to_luv(xyz: (f64, f64, f64)) -> (f64, f64, f64) {
	let (x, y, z) = xyz;
	let l = f(y);

	if l == 0.0 || (xyz == (0.0, 0.0, 0.0)) {
		return (0.0, 0.0, 0.0);
	}

	let var_u = (4.0 * x) / (x + (15.0 * y) + (3.0 *z));
	let var_v = (9.0 * y) / (x + (15.0 * y) + (3.0 *z));
	let u = 13.0 * l * (var_u - REF_U);
	let v = 13.0 * l * (var_v - REF_V);

	(l, u, v)
}

/// Convert RGB to HSLUV
pub fn rgb_to_hsluv(rgb: (f64, f64, f64)) -> (f64, f64, f64) {
	lch_to_hsluv(rgb_to_lch(rgb))
}

/// Convert RGB to HPLUV
pub fn rgb_to_hpluv(rgb: (f64, f64, f64)) -> (f64, f64, f64) {
	lch_to_hpluv(rgb_to_lch(rgb))
}

/// Convert RGB to LCH
pub fn rgb_to_lch(rgb: (f64, f64, f64)) -> (f64, f64, f64) {
	luv_to_lch(
		xyz_to_luv(
			rgb_to_xyz(rgb)
		)
	)
}

/// Convert RGB to XYZ
pub fn rgb_to_xyz(rgb: (f64, f64, f64)) -> (f64, f64, f64) {
	let rgbl = vec![to_linear(rgb.0), to_linear(rgb.1), to_linear(rgb.2)];
	let mapping : Vec<f64> = M_INV.iter().map(|i| dot_product(&i.to_vec(), &rgbl)).collect();
	(mapping[0], mapping[1], mapping[2])
}

/// Convert LUV to LCH
pub fn luv_to_lch(luv: (f64, f64, f64)) -> (f64, f64, f64) {
	let (l, u, v) = luv;
	let c = (u*u + v*v).sqrt();
	if c < 0.00000001 {
		(l, c, 0.0)
	} else {
		let hrad = f64::atan2(v, u);
		let mut h = radians_to_degrees(hrad);
		if h < 0.0 {
			h += 360.0;
		}
		(l, c, h)
	}
}

/// Convert RGB to HEX
pub fn rgb_to_hex(rgb: (f64, f64, f64)) -> String {
	let (r,g,b) = rgb_prepare(rgb);
	format!("#{:02x}{:02x}{:02x}", r,g,b)
}

/// Convert HEX to RGB
pub fn hex_to_rgb(raw_hex: &str) -> (f64, f64, f64) {
	let hex = raw_hex.trim_start_matches('#');
	if hex.len() != 6 {
		println!("Not a hex string!");
		return (0.0,0.0,0.0)
	}
	let mut chunks = hex.as_bytes().chunks(2);
	let red = i64::from_str_radix(str::from_utf8(chunks.next().unwrap()).unwrap(), 16);
	let green = i64::from_str_radix(str::from_utf8(chunks.next().unwrap()).unwrap(), 16);
	let blue = i64::from_str_radix(str::from_utf8(chunks.next().unwrap()).unwrap(), 16);
	( (red.unwrap_or(0) as f64) / 255.0, (green.unwrap_or(0) as f64) / 255.0, (blue.unwrap_or(0) as f64) / 255.0 )
}


fn f_inv(t: f64) -> f64 {
	if t > 8.0 {
		REF_Y * ( (t + 16.0) / 116.0 ).powf(3.0)
	} else {
		REF_Y * t / KAPPA
	}
}

fn to_linear(c: f64) -> f64 {
	if c > 0.04045 {
		( (c + 0.055) / 1.055).powf(2.4)
	} else {
		c / 12.92
	}
}

fn from_linear(c: f64) -> f64 {
	if c <= 0.0031308 {
		12.92 * c
	} else {
		1.055 * (c.powf(1.0/2.4)) - 0.055
	}
}

fn f(t:f64) -> f64 {
	if t > EPSILON {
		116.0 * ( (t / REF_Y).powf(1.0/3.0) ) - 16.0
	} else {
		t / REF_Y * KAPPA
	}
}

fn dot_product(a: &[f64], b: &[f64] ) -> f64 {
	a.iter().zip(b.iter()).map(|(i, j)| i * j).sum()
}

fn rgb_prepare(rgb: (f64, f64, f64)) ->  (u8, u8, u8) {
	(clamp(rgb.0), clamp(rgb.1), clamp(rgb.2))
}

fn clamp(v: f64) -> u8 {
	let mut rounded = (v * 1000.0).round() / 1000.0;
	if rounded < 0.0 {
		rounded = 0.0;
	}
	if rounded > 1.0 {
		rounded = 1.0;
	}
	(rounded * 255.0).round() as u8
}

fn max_chroma_for(l: f64, h: f64) -> f64 {
	let hrad = h / 360.0 * PI * 2.0;

	let mut lengths : Vec<f64> = get_bounds(l)
		.iter()
		.map(|line| length_of_ray_until_intersect(hrad, line))
		.filter(|length| length > &0.0 )
		.collect::<Vec<f64>>();

		lengths.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal) );
		lengths[0]
}

fn max_safe_chroma_for(l: f64) -> f64 {
	let mut lengths = Vec::new();
	get_bounds(l).iter().for_each(|line| {
		let x = intersect_line_line((line.0, line.1), (-1.0/line.0, 0.0) );
		lengths.push(distance_from_pole((x, line.1 + x * line.0)));
	});
	lengths.sort_by(|a,b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
	lengths[0]
}

fn intersect_line_line(line1: (f64, f64), line2: (f64, f64)) -> f64 {
	(line1.1 - line2.1) / (line2.0 - line1.0)
}

fn distance_from_pole(point: (f64, f64)) -> f64 {
	(point.0.powi(2) + point.1.powi(2)).sqrt()
}

fn get_bounds(l: f64) -> Vec<(f64, f64)> {
	let sub1 = ((l + 16.0).powi(3))/ 1560896.0;
	let sub2 = match sub1 {
		s if s > EPSILON => s,
		_ => l / KAPPA
	};

	let mut bounds = Vec::new();

	for ms in &M {
		let (m1, m2, m3) = (ms[0], ms[1], ms[2]);
		for t in 0..2 {
			let top1 = (284517.0 * m1 - 94839.0 * m3) * sub2;
			let top2 = (838422.0 * m3 + 769860.0 * m2 + 731718.0 * m1) * l * sub2 - 769860.0 * f64::from(t) * l;
			let bottom = (632260.0 * m3 - 126452.0 * m2) * sub2 + 126452.0 * f64::from(t);

			bounds.push((top1/bottom, top2/bottom));
		}
	}
	bounds
}

fn length_of_ray_until_intersect(theta: f64, line: &(f64, f64)) -> f64 {
	let (m1, b1) = *line;
	let length = b1 / (theta.sin() - m1 * theta.cos());
	if length < 0.0 {
		-0.0001
	} else {
		length
	}
}

fn radians_to_degrees(rad: f64) -> f64 {
	rad * 180.0 / PI
}

fn degrees_to_radians(deg: f64) -> f64 {
	deg * PI / 180.0
}