main.rs

extern crate image;
extern crate rayon;

use rayon::prelude::*;
use image::ColorType;

fn calculate_point(x : f64, y : f64, depth : usize) -> f32 {
    let mut zx = 0.0;
    let mut zy = 0.0;
    let mut zx1;
    let mut zy1;
    for i in 0 .. depth {
        zx1 = (zx * zx) - (zy * zy) + x;
        zy1 = zx * zy * 2.0 + y;
        if zx1 * zx1 + zy1 * zy1 > 4.0 {
            return (i as f32) / (depth as f32);
        }
        else {
            zx = zx1;
            zy = zy1;
        }
    }
    return 1.0;//depth as f32;
}

const CHANNELS: usize = 3;

fn get_color(colors : &[[f32;3]], buffer : &mut [[f32;3]], x : f32) -> [u8; CHANNELS] {
    let mut len = colors.len() - 1;
    for i in 0 .. len {
        for j in 0 .. 3 {
            buffer[i][j] = colors[i][j] + (colors[i+1][j] - colors[i][j]) * x
        }
    }
    while len > 1 {
        for i in 0 .. len - 1 {
            for j in 0 .. 3 {
                buffer[i][j] = buffer[i][j] + (buffer[i+1][j] - buffer[i][j]) * x
            }
        }
        len -= 1;
    }
    return [buffer[0][0] as u8, buffer[0][1] as u8, buffer[0][2] as u8];
}

fn fill_chunk(buf: &mut [u8], idx0: usize, w: usize, h: usize, colors: &[[f32;3]], color_buf: &mut [[f32;3]]) {
    let mut x = (idx0/CHANNELS) % w;
    let mut y = (idx0/CHANNELS) / w;
    let kx = 2.0 / (w as f64);
    let ky = 2.0 / (h as f64);
    for pv in buf.chunks_mut(CHANNELS) {
        let v = calculate_point(kx*(x as f64) - 1.0, ky*(y as f64) - 1.0, 1000);
        pv.clone_from_slice(&get_color(colors, color_buf, v));
        
        x += 1;
        if x == w { y += 1; x = 0 }
    }
}

fn main() {
    const W: usize = 1000;
    const H: usize = 1000;

    let mut buf = vec![0; W*H*CHANNELS];

    let colors = vec![[0.0,0.0,0.0], [255.0,0.0,0.0], [255.0,255.0,0.0], [255.0,255.0,255.0]];
    buf.par_chunks_mut(W*CHANNELS).enumerate().for_each(|(i, buf)|{
        let colors = &colors;
        let mut color_buf = colors.clone();
        fill_chunk(buf, i*W*CHANNELS, W, H, colors, &mut color_buf);
    });
    
    image::save_buffer("out.png", &buf, W as u32, H as u32, ColorType::RGB(8)).unwrap();
}