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//! Linear orders for colors.
use super::source::ColorSource;
use super::Rgb8;
use crate::hilbert::hilbert_point;
use rand::seq::SliceRandom;
use rand::Rng;
use std::cmp::Ordering;
/// An iterator over all colors from a source.
#[derive(Debug)]
struct ColorSourceIter<S> {
source: S,
coords: Vec<usize>,
}
impl<S: ColorSource> From<S> for ColorSourceIter<S> {
fn from(source: S) -> Self {
let coords = vec![0; source.dimensions().len()];
Self { source, coords }
}
}
impl<S: ColorSource> Iterator for ColorSourceIter<S> {
type Item = Rgb8;
fn next(&mut self) -> Option<Rgb8> {
if self.coords.is_empty() {
return None;
}
let color = self.source.get_color(&self.coords);
let dims = self.source.dimensions();
for i in 0..dims.len() {
self.coords[i] += 1;
if self.coords[i] < dims[i] {
break;
} else if i == dims.len() - 1 {
self.coords.clear();
} else {
self.coords[i] = 0;
}
}
Some(color)
}
}
/// Wrapper for sorting colors by hue.
#[derive(Debug, Eq, PartialEq)]
struct Hue {
/// The quadrant of the hue angle.
quad: i32,
/// The numerator of the hue calculation.
num: i32,
/// The denominator of the hue calculation.
denom: i32,
}
impl From<Rgb8> for Hue {
fn from(rgb8: Rgb8) -> Self {
// The hue angle is atan2(sqrt(3) * (G - B), 2 * R - G - B). We avoid actually computing
// the atan2() as an optimization.
let r = rgb8[0] as i32;
let g = rgb8[1] as i32;
let b = rgb8[2] as i32;
let num = g - b;
let mut denom = 2 * r - g - b;
if num == 0 && denom == 0 {
denom = 1;
}
let quad = match (num >= 0, denom >= 0) {
(true, true) => 0,
(true, false) => 1,
(false, false) => 2,
(false, true) => 3,
};
Self { quad, num, denom }
}
}
impl Ord for Hue {
fn cmp(&self, other: &Self) -> Ordering {
// Within the same quadrant,
//
// atan2(n1, d1) < atan2(n2, d2) iff
// n1 / d1 < n2 / d2 iff
// n1 * d2 < n2 * d1
self.quad
.cmp(&other.quad)
.then_with(|| (self.num * other.denom).cmp(&(other.num * self.denom)))
}
}
impl PartialOrd for Hue {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
/// Iterate over colors sorted by their hue.
pub fn hue_sorted<S: ColorSource>(source: S) -> Vec<Rgb8> {
let mut colors: Vec<_> = ColorSourceIter::from(source).collect();
colors.sort_by_key(|c| Hue::from(*c));
colors
}
/// Iterate over colors in random order.
pub fn shuffled<S: ColorSource, R: Rng>(source: S, rng: &mut R) -> Vec<Rgb8> {
let mut colors: Vec<_> = ColorSourceIter::from(source).collect();
colors.shuffle(rng);
colors
}
/// ceil(log_2(n)). for rounding up to powers of 2.
fn log2(n: usize) -> u32 {
let nbits = 8 * std::mem::size_of::<usize>() as u32;
nbits - (n - 1).leading_zeros()
}
/// Iterate over colors in Morton order (Z-order).
pub fn morton<S: ColorSource>(source: S) -> Vec<Rgb8> {
let mut colors = Vec::new();
let dims = source.dimensions();
let ndims = dims.len();
let nbits = ndims * dims.iter().map(|n| log2(*n) as usize).max().unwrap();
let size = 1usize << nbits;
let mut coords = vec![0; ndims];
for i in 0..size {
for x in &mut coords {
*x = 0;
}
for j in 0..nbits {
let bit = (i >> j) & 1;
coords[j % ndims] |= bit << (j / ndims);
}
if coords.iter().zip(dims.iter()).all(|(x, n)| x < n) {
colors.push(source.get_color(&coords));
}
}
colors
}
/// Iterate over colors in Hilbert curve order.
pub fn hilbert<S: ColorSource>(source: S) -> Vec<Rgb8> {
let mut colors = Vec::new();
let dims = source.dimensions();
let ndims = dims.len();
let bits: Vec<_> = dims.iter().map(|n| log2(*n)).collect();
let nbits: u32 = bits.iter().sum();
let size = 1usize << nbits;
let mut coords = vec![0; ndims];
for i in 0..size {
hilbert_point(i, &bits, &mut coords);
if coords.iter().zip(dims.iter()).all(|(x, n)| x < n) {
colors.push(source.get_color(&coords));
}
}
colors
}
/// Stripe an ordered list of colors, to reduce artifacts in the generated image.
///
/// The striped ordering gives every other item first, then every other item from the remaining
/// items, etc. For example, the striped form of `0..16` is
/// `[0, 2, 4, 6, 8, 10, 12, 14, 1, 5, 9, 13, 3, 11, 7, 15]`.
pub fn striped(colors: Vec<Rgb8>) -> Vec<Rgb8> {
let len = colors.len();
let mut result = Vec::with_capacity(len);
let mut stripe = 1;
while stripe <= len {
for i in ((stripe - 1)..len).step_by(2 * stripe) {
result.push(colors[i]);
}
stripe *= 2;
}
result
}
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