init, implement color quantization

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Crispy 2024-12-04 01:46:45 +01:00
commit 0d8a4e9b0e
4 changed files with 306 additions and 0 deletions

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[package]
name = "dither"
version = "0.1.0"
edition = "2021"
[dependencies]
# image = "0.25.5"
# image = { version = "0.25.5", default-features = false, features = ["default-formats"] }
image = { version = "0.25.5", default-features = false, features = ["jpeg", "png", "webp"] }

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use std::{env, fs::File, io::Read};
use image::{imageops::FilterType, DynamicImage, GenericImage, GenericImageView, Pixel, Rgb};
fn main() {
let mut args: Vec<String> = env::args().skip(1).collect();
if args.is_empty() {
println!("no input file specified");
return;
}
dbg!(&args);
let inpath = args.pop().unwrap();
let mut data = Vec::new();
File::open(inpath).unwrap().read_to_end(&mut data).unwrap();
let image = image::load_from_memory(&data).unwrap();
println!("loaded");
let (w, h) = image.dimensions();
let image = image.resize(w / 8, h / 8, FilterType::CatmullRom);
println!("resized");
let image = dither_limit(image, 2);
image.save("out.png").unwrap();
println!("saved");
}
const BAYER_4x4: [[u8; 4]; 4] = [[0, 8, 2, 10], [12, 4, 14, 6], [3, 11, 1, 9], [15, 7, 13, 5]];
fn bayer_f(x: usize, y: usize) -> f32 {
(BAYER_4x4[y][x] as f32 / 16.) // - (15./16.)/2.
}
fn quantize(image: &DynamicImage, count: usize) -> Vec<Rgb<u8>> {
assert!(count > 0);
let mut buckets: Vec<Vec<Rgb<u8>>> = vec![image
.pixels()
.map(|(_x, _y, a)| a.to_rgb()) //
.collect()];
// divide buckets count-1 times
for _i in 0..(count - 1) {
// spread amount and channel for each bucket
let mut spreads: Vec<(u8, usize)> = Vec::new();
// calculate where each bucket would do its division if it's chosen
// todo: only calculate this when the bucket is created/modified
for bucket in &buckets {
let mut min = [255; 3];
let mut max = [0; 3];
for pixel in bucket {
for channel in 0..3 {
min[channel] = min[channel].min(pixel.0[channel]);
max[channel] = max[channel].max(pixel.0[channel]);
}
}
let range_r = max[0] - min[0];
let range_g = max[1] - min[1];
let range_b = max[2] - min[2];
let mut widest_channel = 0;
let mut widest_amount = range_r;
if range_g > widest_amount {
widest_amount = range_g;
widest_channel = 1;
}
if range_b > widest_amount {
widest_amount = range_b;
widest_channel = 2;
}
spreads.push((widest_amount, widest_channel))
}
let mut most_spread_bucket = 0;
let mut highest_spread = 0;
for (i, &(spread, _channel)) in spreads.iter().enumerate() {
if spread > highest_spread {
most_spread_bucket = i;
highest_spread = spread;
}
}
// divide the most spread bucket
let bucket = &mut buckets[most_spread_bucket];
if bucket.len() < 2 {
continue;
}
let channel = spreads[most_spread_bucket].1;
bucket.sort_unstable_by_key(|pixel| pixel.0[channel]);
let halfway = bucket.len() / 2;
let new_bucket = bucket[halfway..].to_owned();
bucket.truncate(halfway);
buckets.push(new_bucket);
}
let mut colors = Vec::new();
for bucket in buckets {
let mut avg = [0u128; 3];
for p in &bucket {
for channel in 0..3 {
avg[channel] += p.0[channel] as u128;
}
}
let num = bucket.len() as u128;
colors.push(Rgb([
(avg[0] / num) as u8,
(avg[1] / num) as u8,
(avg[2] / num) as u8,
]))
}
colors
}
fn color_dist(a: Rgb<u8>, b: Rgb<u8>) -> f32 {
let r = a.0[0] as f32 - b.0[0] as f32;
let g = a.0[1] as f32 - b.0[1] as f32;
let b = a.0[2] as f32 - b.0[2] as f32;
(r * r + g * g + b * b).sqrt()
}
fn dither_limit(input: DynamicImage, count: usize) -> DynamicImage {
let colors = quantize(&input, count);
let mut out = input.clone();
for (x, y, color) in input.pixels() {
let color = color.to_rgb();
let mut closest_index = 0;
let mut closest_dist = color_dist(color, colors[0]);
for (i, &c) in colors.iter().enumerate() {
let d = color_dist(color, c);
if d < closest_dist {
closest_dist = d;
closest_index = i;
}
}
out.put_pixel(x, y, colors[closest_index].to_rgba());
}
out
}