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-rw-r--r--src/color.rs1
-rw-r--r--src/color/order.rs196
-rw-r--r--src/hilbert.rs136
-rw-r--r--src/main.rs1
4 files changed, 334 insertions, 0 deletions
diff --git a/src/color.rs b/src/color.rs
index e0a3399..64fd82b 100644
--- a/src/color.rs
+++ b/src/color.rs
@@ -1,5 +1,6 @@
//! Colors and color spaces.
+pub mod order;
pub mod source;
use crate::metric::kd::{Cartesian, CartesianMetric};
diff --git a/src/color/order.rs b/src/color/order.rs
new file mode 100644
index 0000000..300a556
--- /dev/null
+++ b/src/color/order.rs
@@ -0,0 +1,196 @@
+//! 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
+}
diff --git a/src/hilbert.rs b/src/hilbert.rs
new file mode 100644
index 0000000..c0982d4
--- /dev/null
+++ b/src/hilbert.rs
@@ -0,0 +1,136 @@
+//! Implementation of [Compact Hilbert Indices](https://dl.acm.org/doi/10.1109/CISIS.2007.16) by
+//! Chris Hamilton.
+
+/// Right rotation of x by b bits out of n.
+fn rotate_right(x: usize, b: u32, n: u32) -> usize {
+ let l = x & ((1 << b) - 1);
+ let r = x >> b;
+ (l << (n - b)) | r
+}
+
+/// Left rotation of x by b bits out of n.
+fn rotate_left(x: usize, b: u32, n: u32) -> usize {
+ rotate_right(x, n - b, n)
+}
+
+/// Binary reflected Gray code.
+fn gray_code(i: usize) -> usize {
+ i ^ (i >> 1)
+}
+
+/// e(i), the entry point for the ith sub-hypercube.
+fn entry_point(i: usize) -> usize {
+ if i == 0 {
+ 0
+ } else {
+ gray_code((i - 1) & !1)
+ }
+}
+
+/// g(i), the inter sub-hypercube direction.
+fn inter_direction(i: usize) -> u32 {
+ // g(i) counts the trailing set bits in i
+ (!i).trailing_zeros()
+}
+
+/// d(i), the intra sub-hypercube direction.
+fn intra_direction(i: usize) -> u32 {
+ if i & 1 != 0 {
+ inter_direction(i)
+ } else if i > 0 {
+ inter_direction(i - 1)
+ } else {
+ 0
+ }
+}
+
+/// T transformation inverse
+fn t_inverse(dims: u32, e: usize, d: u32, a: usize) -> usize {
+ rotate_left(a, d, dims) ^ e
+}
+
+/// GrayCodeRankInverse
+fn gray_code_rank_inverse(
+ dims: u32,
+ mu: usize,
+ pi: usize,
+ r: usize,
+ free_bits: u32,
+) -> (usize, usize) {
+ // The inverse rank of r
+ let mut i = 0;
+ // gray_code(i)
+ let mut g = 0;
+
+ let mut j = free_bits - 1;
+ for k in (0..dims).rev() {
+ if mu & (1 << k) == 0 {
+ g |= pi & (1 << k);
+ i |= (g ^ (i >> 1)) & (1 << k);
+ } else {
+ i |= ((r >> j) & 1) << k;
+ g |= (i ^ (i >> 1)) & (1 << k);
+ j = j.wrapping_sub(1);
+ }
+ }
+
+ (i, g)
+}
+
+/// ExtractMask.
+fn extract_mask(bits: &[u32], i: u32) -> (usize, u32) {
+ // The mask
+ let mut mu = 0;
+ // popcount(mu)
+ let mut free_bits = 0;
+
+ let dims = bits.len();
+ for j in (0..dims).rev() {
+ mu <<= 1;
+ if bits[j] > i {
+ mu |= 1;
+ free_bits += 1;
+ }
+ }
+
+ (mu, free_bits)
+}
+
+/// Compute the corresponding point for a Hilbert index (CompactHilbertIndexInverse).
+pub fn hilbert_point(index: usize, bits: &[u32], point: &mut [usize]) {
+ let dims = bits.len() as u32;
+ let max = *bits.iter().max().unwrap();
+ let sum: u32 = bits.iter().sum();
+
+ let mut e = 0;
+ let mut k = 0;
+
+ // Next direction; we use d instead of d + 1 everywhere
+ let mut d = 1;
+
+ for x in point.iter_mut() {
+ *x = 0;
+ }
+
+ for i in (0..max).rev() {
+ let (mut mu, free_bits) = extract_mask(bits, i);
+ mu = rotate_right(mu, d, dims);
+
+ let pi = rotate_right(e, d, dims) & !mu;
+
+ let r = (index >> (sum - k - free_bits)) & ((1 << free_bits) - 1);
+
+ k += free_bits;
+
+ let (w, mut l) = gray_code_rank_inverse(dims, mu, pi, r, free_bits);
+ l = t_inverse(dims, e, d, l);
+
+ for x in point.iter_mut() {
+ *x |= (l & 1) << i;
+ l >>= 1;
+ }
+
+ e = e ^ rotate_right(entry_point(w), d, dims);
+ d = (d + intra_direction(w) + 1) % dims;
+ }
+}
diff --git a/src/main.rs b/src/main.rs
index a7bda67..a59a0cf 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
pub mod color;
+pub mod hilbert;
pub mod metric;
fn main() {}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-22 16:23:04 +0000