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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2aff81306fcac3c7515ad4e177f521b5c9a15f2b08f4e32d823066102f35a5f6"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-backend",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.84"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0046fef7e28c3804e5e38bfa31ea2a0f73905319b677e57ebe37e49358989b5d"
+
+[[package]]
+name = "weezl"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9193164d4de03a926d909d3bc7c30543cecb35400c02114792c2cae20d5e2dbb"
+
+[[package]]
+name = "zune-inflate"
+version = "0.2.53"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "440a08fd59c6442e4b846ea9b10386c38307eae728b216e1ab2c305d1c9daaf8"
+dependencies = [
+ "simd-adler32",
+]
--- /dev/null
+use std::fs::File;
+
+use image::{codecs::png::PngEncoder, ColorType, ImageEncoder};
+use num::Complex;
+use rayon::prelude::{IntoParallelIterator, ParallelIterator};
+
+// Page 508.
+pub fn mandelbrot() {
+ println!("===== rayon =====");
+
+ let width = 1920;
+ let height = 1080;
+ let upper_left = Complex { re: -1.2, im: 0.35 };
+ let lower_right = Complex { re: -1.0, im: 0.2 };
+
+ let mut pixels = vec![0; width * height];
+ let bands: Vec<(usize, &mut [u8])> = pixels.chunks_mut(width).enumerate().collect();
+
+ bands.into_par_iter().for_each(|(i, band)| {
+ let top = i;
+ let band_bounds = (width, 1);
+ let band_upper_left = pixel_to_point((width, height), (0, top), upper_left, lower_right);
+ let band_lower_right =
+ pixel_to_point((width, height), (width, top + 1), upper_left, lower_right);
+ render(band, band_bounds, band_upper_left, band_lower_right);
+ });
+
+ write_image("output.png", &pixels, (width, height)).unwrap();
+}
+
+// page 32.
+fn render(
+ pixels: &mut [u8],
+ bounds: (usize, usize),
+ upper_left: Complex<f64>,
+ lower_right: Complex<f64>,
+) {
+ assert!(pixels.len() == bounds.0 * bounds.1);
+
+ for row in 0..bounds.1 {
+ for column in 0..bounds.0 {
+ let point = pixel_to_point(bounds, (column, row), upper_left, lower_right);
+ pixels[row * bounds.0 + column] = match escape_time(point, 255) {
+ None => 0,
+ Some(count) => 255 - count as u8,
+ };
+ }
+ }
+}
+
+fn escape_time(c: Complex<f64>, limit: usize) -> Option<usize> {
+ let mut z = Complex { re: 0.0, im: 0.0 };
+ for i in 0..limit {
+ if z.norm_sqr() > 4.0 {
+ return Some(i);
+ }
+ z = z * z + c;
+ }
+ None
+}
+
+fn pixel_to_point(
+ bounds: (usize, usize),
+ pixel: (usize, usize),
+ upper_left: Complex<f64>,
+ lower_right: Complex<f64>,
+) -> Complex<f64> {
+ let (width, height) = (
+ lower_right.re - upper_left.re,
+ upper_left.im - lower_right.im,
+ );
+ Complex {
+ re: upper_left.re + pixel.0 as f64 * width / bounds.0 as f64,
+ im: upper_left.im - pixel.1 as f64 * height / bounds.1 as f64,
+ }
+}
+
+fn write_image(
+ filename: &str,
+ pixels: &[u8],
+ bounds: (usize, usize),
+) -> Result<(), std::io::Error> {
+ let output = File::create(filename)?;
+ let encoder = PngEncoder::new(output);
+ encoder
+ .write_image(&pixels, bounds.0 as u32, bounds.1 as u32, ColorType::L8)
+ .unwrap(); // TODO: use '?'.
+
+ Ok(())
+}