Midpoint circle algorithm

drawcircle.rs

/// implemention of http://groups.csail.mit.edu/graphics/classes/6.837/F98/Lecture6/circle.html

use std::fs::File;
use std::path::Path;

use image::{self, GenericImage, ImageBuffer, Pixel, Rgba};

struct Point {
    x: u32,
    y: u32
}

pub struct Picture {
    buffer: Box< ImageBuffer<Rgba<u8>, Vec<u8>> >,
    height: u32,
    width: u32
}

fn set_circle_point(pic: &mut Picture, center_pt: &Point, line_pt: &Point, color: u8){
    let act = Rgba::from_channels(255, 0, 0, 255);
    let pix = Rgba::from_channels(255, 0, color, 255);
    let ref mut buf = &mut pic.buffer;

    if line_pt.x == 0 {
        buf.put_pixel(center_pt.x, center_pt.y + line_pt.y, act );
        buf.put_pixel(center_pt.x, center_pt.y - line_pt.y, pix);
        buf.put_pixel(center_pt.x + line_pt.y, line_pt.y, pix);
        buf.put_pixel(center_pt.x - line_pt.y, line_pt.y, pix);

    } else if line_pt.x == line_pt.y {
        buf.put_pixel(center_pt.x + line_pt.x, center_pt.y + line_pt.y, act);
        buf.put_pixel(center_pt.x - line_pt.x, center_pt.y + line_pt.y, pix);
        buf.put_pixel(center_pt.x + line_pt.x, center_pt.y - line_pt.y, pix);
        buf.put_pixel(center_pt.x - line_pt.x, center_pt.y - line_pt.y, pix);
    } else if line_pt.x < line_pt.y {
        buf.put_pixel(center_pt.x + line_pt.x, center_pt.y + line_pt.y, act);
        buf.put_pixel(center_pt.x - line_pt.x, center_pt.y + line_pt.y, pix);
        buf.put_pixel(center_pt.x + line_pt.x, center_pt.y - line_pt.y, pix);
        buf.put_pixel(center_pt.x - line_pt.x, center_pt.y - line_pt.y, pix);
        buf.put_pixel(center_pt.x + line_pt.y, center_pt.y + line_pt.x, pix);
        buf.put_pixel(center_pt.x - line_pt.y, center_pt.y + line_pt.x, pix);
        buf.put_pixel(center_pt.x + line_pt.y, center_pt.y - line_pt.x, pix);
        buf.put_pixel(center_pt.x - line_pt.y, center_pt.y - line_pt.x, pix);
    }
}


fn draw(pic: &mut Picture, center_pt: Point, radius: u32, color: u8) {
    let mut start_pt = Point {x: 0, y: radius};
    let r:i32 = radius as i32;
    let mut p:i32 = ( 5 - r * 4) / 4;

    set_circle_point(pic, &center_pt, &start_pt, color);
    while start_pt.x < start_pt.y {
        start_pt.x += 1;
        println!("P: {}", p);
        if p < 0 {
            p += (2 * start_pt.x + 1) as i32;
        } else {
            start_pt.y -= 1;
            p += (2 * ( (start_pt.x as i32) - (start_pt.y as i32) )  + 1) as i32;
        }

        set_circle_point(pic, &center_pt, &start_pt, color);
    }

}

#[test]
fn save_test_image(){
    let (w, h) = (512,512);
    let mut buf = ImageBuffer::new(w, h);
    let mut pic = Picture { buffer: Box::new(buf), width: w, height: h};
    let center_point = Point {x: 255, y: 255};
    let radius = 128;
    let color = 64u8;

    draw(&mut pic, center_point, radius, color);

    let ref mut fout = File::create(&Path::new("circle.png")).unwrap();
    image::ImageRgba8(*pic.buffer).save(fout, image::PNG).unwrap();

    assert!(true);
}