fn main() {
    let width = 500;
    let height = 5000;
    let mut total = 0.0;
    let mut collection =vec![255;width*height*4];
    for i in 0..20 {
        println!("round {}",i);
        let now = SystemTime::now();
        for j in 0..height {
            for i in 0..width {
                if i  > width/4 && i < width*3/4 {
                    collection[i + j*width*4] = 0;
                    collection[i+j*width*4 + 1] = 0;
                    collection[i+j*width*4 +2] = 0;
                }
            }
        }
        total += now.elapsed().unwrap().as_millis() as f64;
    }
    println!("20 runs took {} total for each  {}",total,total/20.0) ;

    println!("merge 20 20 {:?}",merge(20,20));
    for i in 0..20 {
        // merge height lines
        let mut collection = vec![255; width * height * 4]; //rgba for each pixel
        println!("round {}",i);
        let now = SystemTime::now();
        // skips four lines takes the next 8
        //for pixel in collection.chunks_mut(4 * width).skip(4).take(8).flat_map(|line| line[4 * 4 .. 12 * 4].chunks_mut(4)) {
        for pixel in collection.chunks_mut(4 * width).flat_map(|line| line[width/4 * 4 .. width*3/4 * 4].chunks_mut(4)) {
            pixel[.. 3].copy_from_slice(&[0, 0, 0]);
        }
        total +=now.elapsed().unwrap().as_millis() as f64;
    }
    println!("20 runs took {} total for each  {}",total,total/20.0) ;
    // make a black square in the middle
    // canvas is 16x16 go from 4 to 12 for each
}