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-rw-r--r--src/main.rs91
1 files changed, 91 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..8196108
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,91 @@
+use async_std::{fs::File, io, prelude::*, task, io::BufWriter};
+
+fn lerp(fraction: f64, from: f64, to: f64) -> f64 {
+ from + fraction * (to - from)
+}
+
+fn compute_pixel(re: f64, im: f64) -> u32 {
+ let mut a = re;
+ let mut b = im;
+ let mut a2 = a * a;
+ let mut b2 = b * b;
+ let mut niters = 0;
+ while a2 + b2 < 4.0 {
+ b = 2.0 * a * b + im;
+ a = a2 - b2 + re;
+ a2 = a * a;
+ b2 = b * b;
+ niters += 1;
+ if niters >= 10240 { break; }
+ }
+ niters
+}
+
+async fn compute_row(im: f64, re_min: f64, re_max: f64, width: usize) -> Vec<u32> {
+ let mut row = Vec::new();
+ row.resize(width, 0);
+ for i in 0..width {
+ row[i] = compute_pixel(lerp((i as f64) / (width as f64), re_min, re_max), im);
+ }
+ row
+}
+
+async fn write_image(fname: &str, rows: &Vec<Vec<u32>>) -> io::Result<()> {
+ let width = rows[0].len();
+ let height = rows.len();
+ let maxval = rows.iter().map(|row| row.iter().max().unwrap()).max().unwrap();
+
+ let mut out_vec: Vec<u8> = Vec::new();
+ let mut writer = BufWriter::new(&mut out_vec);
+ write!(writer, "P2\n{} {}\n{}\n", width, height, maxval).await?;
+ for row in rows {
+ for item in row {
+ write!(writer, "{} ", item).await?;
+ }
+ writeln!(writer).await?;
+ }
+
+ let mut file = File::create(fname).await?;
+ file.write(&out_vec).await?;
+ file.flush().await?;
+
+ Ok(())
+}
+
+async fn compute_brot(fname: &str, width: usize, height: usize, left_top: (f64, f64), right_bottom: (f64, f64)) -> io::Result<()> {
+ println!("Spawning...");
+ let mut join_handles = Vec::with_capacity(height);
+ for i in 0..height {
+ let im = lerp(i as f64 / height as f64, left_top.1, right_bottom.1);
+ // Note: spawn to not run within the same thread
+ join_handles.push(task::spawn(compute_row(im, left_top.0, right_bottom.0, width)));
+ }
+
+ println!("Awaiting...");
+ let mut rows = Vec::with_capacity(height);
+ for jh in join_handles {
+ rows.push(jh.await);
+ }
+
+ println!("Writing...");
+ write_image(fname, &rows).await
+}
+
+fn main() -> io::Result<()> {
+ // Note: the following does not work:
+ // task::block_on(task::spawn(compute_brot("out.ppm", 1920, 1080, (-1.5, 1.0), (1.0, -1.0))))
+ // You get a scary large futures error about Send.
+
+ task::block_on(async {
+ let width = 1920;
+ let height = 1080;
+ let left = -1.8;
+ let right = 1.5;
+ let height_im = height as f64 / width as f64 * (right - left);
+ let top = height_im / 2.0;
+ let bottom = -height_im / 2.0;
+ compute_brot("out.ppm", width, height, (left, top), (right, bottom)).await
+ })
+}
+
+// vim: set sw=4 ts=4 et: