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Merge pull request #5458 from vangel76/perf/5454-trace-smooth-weight-table

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Trace: look up the smoothing weights instead of computing them per pixel (#5454)
This commit is contained in:
BFlat
2026-11-04 09:19:50 +07:00
committed by GitHub
parent 9705a6056c f75616af54
commit ae5f581615
2 changed files with 156 additions and 12 deletions
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contributors/people.toml
+5
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@@ -193,3 +193,8 @@ sync_github_name = true
[people.JonRC]
real_name = "Jonathan Cardoso"
display_name = "Jonathan Cardoso"
[people.vangel76]
real_name = "Valentin Klein"
display_name = "vangel76"
sync_github_name = false
crates/trace/src/smooth.rs
+151 -12
View File
@@ -13,33 +13,54 @@ use crate::{Raster, parallel_map};
/// Colours this far apart (levels, all channels together) count half as much as equal ones.
const ALIKE: f64 = 20.0;
/// One pass along rows (`dx = 1`) or columns (`dx = 0`).
fn pass(src: &[u8], w: usize, h: usize, along_rows: bool) -> Vec<u8> {
/// How much a neighbour counts, by the squared distance between the two colours (all channels
/// together): `1 / (1 + d2 / ALIKE²)²`. Distances are whole numbers, so every value a pass can ask
/// for is worked out once here instead of once per pixel and neighbour.
fn weight_table() -> Vec<f64> {
(0..=3 * 255 * 255usize).map(|d2| 1.0 / (1.0 + d2 as f64 / (ALIKE * ALIKE)).powi(2)).collect()
}
/// `v` rounded to the nearest level, halves up. The same as `v.round() as u8` for `0 <= v <= 255`,
/// without the library call that `round` is on targets that lack a rounding instruction.
fn level(v: f64) -> u8 {
let whole = v as u8;
whole.saturating_add(u8::from(v - f64::from(whole) >= 0.5))
}
/// The pixel at column `x` of `row`.
fn at(row: &[u8], x: usize) -> Option<&[u8]> {
row.get(x * 4..x * 4 + 4)
}
/// One pass along rows (`dx = 1`) or columns (`dx = 0`), weighting by `weights` (see `weight_table`).
fn pass(src: &[u8], w: usize, h: usize, along_rows: bool, weights: &[f64]) -> Vec<u8> {
let rows: Vec<usize> = (0..h).collect();
let px = |x: usize, y: usize| src.get((y * w + x) * 4..(y * w + x) * 4 + 4);
let row = |y: usize| src.get(y * w * 4..(y + 1) * w * 4).unwrap_or_default();
let done = parallel_map(&rows, |&y| {
let cur = row(y);
let (above, below) = (y.checked_sub(1).map(row), (y + 1 < h).then(|| row(y + 1)));
let mut out = Vec::with_capacity(w * 4);
for x in 0..w {
let Some(p) = px(x, y) else { continue };
for (x, p) in cur.as_chunks::<4>().0.iter().enumerate() {
if p[3] < 128 {
out.extend_from_slice(p);
continue;
}
let near = if along_rows {
[(x > 0).then(|| (x - 1, y)), (x + 1 < w).then(|| (x + 1, y))]
[x.checked_sub(1).and_then(|x| at(cur, x)), at(cur, x + 1)]
} else {
[(y > 0).then(|| (x, y - 1)), (y + 1 < h).then(|| (x, y + 1))]
[above.and_then(|r| at(r, x)), below.and_then(|r| at(r, x))]
};
let (mut sum, mut weight) = ([f64::from(p[0]), f64::from(p[1]), f64::from(p[2])], 1.0);
for q in near.into_iter().flatten().filter_map(|(x, y)| px(x, y)).filter(|q| q[3] >= 128) {
let d2: f64 = (0..3).map(|k| (f64::from(q[k]) - f64::from(p[k])).powi(2)).sum();
let wt = 1.0 / (1.0 + d2 / (ALIKE * ALIKE)).powi(2);
for q in near.into_iter().flatten().filter(|q| q[3] >= 128) {
let d = |k: usize| i32::from(q[k]) - i32::from(p[k]);
let d2 = (d(0) * d(0) + d(1) * d(1) + d(2) * d(2)) as usize;
let wt = weights.get(d2).copied().unwrap_or(0.0);
for k in 0..3 {
sum[k] += wt * f64::from(q[k]);
}
weight += wt;
}
out.extend(sum.map(|v| (v / weight).round() as u8));
out.extend(sum.map(|v| level(v / weight)));
out.push(p[3]);
}
out
@@ -52,8 +73,9 @@ pub(crate) fn smoothed(img: &Raster) -> Raster {
let (w, h) = (img.width as usize, img.height as usize);
let mut rgba = img.rgba.clone();
if rgba.len() == w * h * 4 {
let weights = weight_table();
for _ in 0..3 {
rgba = pass(&pass(&rgba, w, h, true), w, h, false);
rgba = pass(&pass(&rgba, w, h, true, &weights), w, h, false, &weights);
}
}
Raster { width: img.width, height: img.height, rgba }
@@ -85,6 +107,123 @@ mod tests {
assert!(out.pixel(19, 10)[0] < 70 && out.pixel(20, 10)[0] > 150);
}
/// The filter as it was before the weight table: the reference the fast pass must match byte for byte.
fn reference(src: &[u8], w: usize, h: usize, along_rows: bool) -> Vec<u8> {
let px = |x: usize, y: usize| src.get((y * w + x) * 4..(y * w + x) * 4 + 4);
let mut out = Vec::with_capacity(w * h * 4);
for y in 0..h {
for x in 0..w {
let Some(p) = px(x, y) else { continue };
if p[3] < 128 {
out.extend_from_slice(p);
continue;
}
let near = if along_rows {
[(x > 0).then(|| (x - 1, y)), (x + 1 < w).then(|| (x + 1, y))]
} else {
[(y > 0).then(|| (x, y - 1)), (y + 1 < h).then(|| (x, y + 1))]
};
let (mut sum, mut weight) = ([f64::from(p[0]), f64::from(p[1]), f64::from(p[2])], 1.0);
for q in near.into_iter().flatten().filter_map(|(x, y)| px(x, y)).filter(|q| q[3] >= 128) {
let d2: f64 = (0..3).map(|k| (f64::from(q[k]) - f64::from(p[k])).powi(2)).sum();
let wt = 1.0 / (1.0 + d2 / (ALIKE * ALIKE)).powi(2);
for k in 0..3 {
sum[k] += wt * f64::from(q[k]);
}
weight += wt;
}
out.extend(sum.map(|v| (v / weight).round() as u8));
out.push(p[3]);
}
}
out
}
fn reference_smoothed(img: &Raster) -> Vec<u8> {
let (w, h) = (img.width as usize, img.height as usize);
let mut rgba = img.rgba.clone();
for _ in 0..3 {
rgba = reference(&reference(&rgba, w, h, true), w, h, false);
}
rgba
}
fn hash(x: u32, y: u32, salt: u32) -> u32 {
let mut n = x.wrapping_mul(0x9E37_79B1) ^ y.wrapping_mul(0x85EB_CA77) ^ salt.wrapping_mul(0xC2B2_AE3D);
n ^= n >> 15;
n = n.wrapping_mul(0x2C1B_3C6D);
n ^= n >> 13;
n.wrapping_mul(0x297A_2D39) ^ (n >> 16)
}
#[test]
fn same_bytes_as_the_unoptimised_filter() {
let inputs: Vec<(&str, Raster)> = vec![
("random colours", Raster::from_fn(61, 47, |x, y| [hash(x, y, 1) as u8, (hash(x, y, 2) >> 3) as u8, (hash(x, y, 3) >> 5) as u8, 255])),
(
"photo-like",
Raster::from_fn(90, 70, |x, y| {
let base = ((x as f64 / 9.0).sin() * 60.0 + (y as f64 / 13.0).cos() * 60.0 + 128.0) as i32;
let v = (base + (hash(x, y, 4) % 9) as i32 - 4).clamp(0, 255) as u8;
[v, (i32::from(v) / 2 + 60) as u8, 255 - v, 255]
}),
),
("gradient", Raster::from_fn(80, 33, |x, y| [(x * 3) as u8, (y * 7) as u8, (x + y) as u8, 255])),
("flat", Raster::from_fn(20, 20, |_, _| [40, 90, 200, 255])),
("extremes", Raster::from_fn(32, 32, |x, y| if hash(x, y, 5).is_multiple_of(2) { [0, 0, 0, 255] } else { [255, 255, 255, 255] })),
(
"holes and half alpha",
Raster::from_fn(50, 40, |x, y| {
[hash(x, y, 6) as u8, (hash(x, y, 7) >> 8) as u8, 77, [0, 127, 128, 255, 255][(hash(x, y, 8) % 5) as usize]]
}),
),
("one column", Raster::from_fn(1, 30, |_, y| [(y * 8) as u8, 5, 9, 255])),
("one row", Raster::from_fn(30, 1, |x, _| [(x * 8) as u8, 5, 9, 255])),
("one pixel", Raster::from_fn(1, 1, |_, _| [1, 2, 3, 255])),
("two by two", Raster::from_fn(2, 2, |x, y| [(x * 100) as u8, (y * 100) as u8, 3, 255])),
("wide", Raster::from_fn(257, 3, |x, y| [x as u8, (x / 2) as u8, y as u8, 255])),
];
for (name, img) in &inputs {
assert_eq!(smoothed(img).rgba, reference_smoothed(img), "{name}");
}
}
#[test]
fn same_bytes_for_every_pair_of_grey_levels() {
// Every pixel next to every possible neighbour, one table for all of them (the picture
// tests above run the three rounds).
let weights = weight_table();
for p in 0..=255u8 {
for q in 0..=255u8 {
// Grey, and a mixed pair, along a row (2x1) and along a column (1x2).
for src in [[p, p, p, 255, q, q, q, 255], [p, q, p ^ q, 255, q, p, q ^ 0x5a, 255]] {
assert_eq!(pass(&src, 2, 1, true, &weights), reference(&src, 2, 1, true), "{p} {q}");
assert_eq!(pass(&src, 1, 2, false, &weights), reference(&src, 1, 2, false), "{p} {q}");
}
}
}
}
#[test]
fn level_is_round_for_every_value_that_can_occur() {
for v in
[0.0, 0.499_999_999_999_999_94, 0.5, 0.500_000_000_000_000_1, 1.499_999_999_999_999_8, 1.5, 127.5, 254.5, 254.999_999_999_999_97, 255.0]
{
assert_eq!(level(v), v.round() as u8, "{v}");
}
// Values a hair either side of every half, where a wrong rounding would show.
for k in 0..255 {
let half = f64::from(k) + 0.5;
for v in [half, f64::from_bits(half.to_bits() - 1), f64::from_bits(half.to_bits() + 1)] {
assert_eq!(level(v), v.round() as u8, "{v}");
}
}
for i in 0..=255 * 4096u32 {
let v = f64::from(i) / 4096.0;
assert_eq!(level(v), v.round() as u8, "{v}");
}
}
#[test]
fn transparent_pixels_and_odd_sizes_pass_through() {
let img = Raster::from_fn(3, 1, |x, _| [10 * x as u8, 0, 0, if x == 1 { 0 } else { 255 }]);