Function normalize_triangle 

pub fn normalize_triangle(
    width: usize,
    height: usize,
    x1: i32,
    y1: i32,
    x2: i32,
    y2: i32,
    x3: i32,
    y3: i32,
) -> Option<NormalizedTriangle>

The point of this function is to produce two ranges left_x..=right_x and top_y..=bottom_y that are guaranteed to be safe to iterate over the canvas of size width by height without any boundary checks.