lr -> pr

pr/ch2/mandelbrot/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "mandelbrot"
+version = "0.1.0"
+authors = ["Kyle Isom <kyle@imap.cc>"]
+
+[dependencies]
+crossbeam = "0.2.8"
+image = "0.13.0"
+num = "0.1.27"

pr/ch2/mandelbrot/src/main.rs

@@ -0,0 +1,165 @@
+extern crate crossbeam;
+extern crate image;
+extern crate num;
+
+use image::png::PNGEncoder;
+use image::ColorType;
+use num::Complex;
+use std::fs::File;
+use std::io::Write;
+use std::str::FromStr;
+
+#[allow(dead_code)]
+
+fn parse_pair<T: FromStr>(s: &str, separator: char) -> Option<(T, T)> {
+    match s.find(separator) {
+        None => None,
+        Some(index) => match (T::from_str(&s[..index]), T::from_str(&s[index + 1..])) {
+            (Ok(l), Ok(r)) => Some((l, r)),
+            _ => None,
+        },
+    }
+}
+
+fn parse_complex(s: &str) -> Option<Complex<f64>> {
+    match parse_pair(s, ',') {
+        Some((re, im)) => Some(Complex { re, im }),
+        None => None,
+    }
+}
+
+#[test]
+fn test_parse_complex() {
+    assert_eq!(
+        parse_complex("1.25,-0.0625"),
+        Some(Complex {
+            re: 1.25,
+            im: -0.0625
+        })
+    );
+    assert_eq!(parse_complex(",-0.0625", None))
+}
+
+fn escape_time(c: Complex<f64>, limit: u32) -> Option<u32> {
+    let mut z = Complex { re: 0.0, im: 0.0 };
+    for i in 0..limit {
+        z = z * z + c;
+        if z.norm_sqr() > 4.0 {
+            return Some(i);
+        }
+    }
+
+    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,
+        // Subtraction because pixel.1 increases downward, but the imaginary
+        // component increases upward.
+        im: upper_left.im - pixel.1 as f64 * height / bounds.1 as f64,
+    }
+}
+
+#[test]
+fn test_pixel_to_point() {
+    assert_eq!(
+        pixel_to_point(
+            (100, 100),
+            (25, 75),
+            Complex { re: -1.0, im: 1.0 },
+            Complex { re: 1.0, im: -1.0 }
+        ),
+        Complex { re: -0.5, im: -0.5 }
+    );
+}
+
+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.1 {
+            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 write_image(
+    filename: &str,
+    pixels: &[u8],
+    bounds: (usize, usize),
+) -> Result<(), std::io::Error> {
+    let output = File::create(filename)?;
+
+    let encoder = PNGEncoder::new(output);
+    encoder.encode(
+        &pixels,
+        bounds.0 as u32,
+        bounds.1 as u32,
+        ColorType::Gray(8),
+    )?;
+    Ok(())
+}
+
+fn main() {
+    let args: Vec<String> = std::env::args().collect();
+
+    if args.len() != 5 {
+        writeln!(
+            std::io::stderr(),
+            "Usage: mandelbrot FILE PIXELS UPPERLEFT LOWERRIGHT"
+        ).unwrap();
+        writeln!(
+            std::io::stderr(),
+            "Example: {} mandel.png 1000x750 -1.20,0.35 -1,0.20",
+            args[0]
+        ).unwrap();
+        std::process::exit(1);
+    }
+
+    let bounds: (usize, usize) = parse_pair(&args[2], 'x').expect("error parsing image dimensions");
+    let upper_left = parse_complex(&args[3]).expect("error parsing upper left corner point");
+    let lower_right = parse_complex(&args[4]).expect("error parsing lower right corner point");
+
+    let mut pixels = vec![0; bounds.0 * bounds.1];
+
+    let threads = 8;
+    let rows_per_band = bounds.1 / threads + 1;
+    {
+        let bands: Vec<&mut [u8]> = pixels.chunks_mut(rows_per_band * bounds.0).collect();
+        crossbeam::scope(|spawner| {
+            for (i, band) in bands.into_iter().enumerate() {
+                let top = rows_per_band * i;
+                let height = band.len() / bounds.0;
+                let band_bounds = (bounds.0, height);
+                let band_upper_left = pixel_to_point(bounds, (0, top), upper_left, lower_right);
+                let band_lower_right =
+                    pixel_to_point(bounds, (bounds.0, top + height), upper_left, lower_right);
+
+                spawner.spawn(move || {
+                    println!("spawned: {}", i);
+                    render(band, band_bounds, band_upper_left, band_lower_right);
+                });
+            }
+        });
+    }
+    write_image(&args[1], &pixels, bounds).expect("error writing PNG file");
+}