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use super::Image;
#[allow(dead_code)]
pub trait CenterOfMass {
/// The center of mass.
///
/// Ignores pixels that are zero.
///
/// Only considers non-zero pixels and assign them `mass = 1`.
///
/// https://en.wikipedia.org/wiki/Center_of_mass
fn center_of_mass(&self, scale: u32) -> Option<(u32, u32)>;
}
impl CenterOfMass for Image {
fn center_of_mass(&self, scale: u32) -> Option<(u32, u32)> {
if self.is_empty() {
return None;
}
let mut sum_x: u32 = 0;
let mut sum_y: u32 = 0;
let mut mass: u16 = 0;
for y in 0..self.height() {
for x in 0..self.width() {
if self.get(x as i32, y as i32).unwrap_or(0) == 0 {
continue;
}
mass += 1;
sum_x += x as u32;
sum_y += y as u32;
}
}
if mass == 0 {
return None;
}
let center_x: u32 = sum_x * scale / (mass as u32);
let center_y: u32 = sum_y * scale / (mass as u32);
Some((center_x, center_y))
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::arc::ImageTryCreate;
#[test]
fn test_10000_centered() {
// Arrange
let pixels: Vec<u8> = vec![
1, 1,
1, 1,
];
let input: Image = Image::try_create(2, 2, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (500, 500));
}
#[test]
fn test_10001_centered() {
// Arrange
let pixels: Vec<u8> = vec![
0, 1, 1, 0,
1, 0, 0, 1,
1, 0, 0, 1,
0, 1, 1, 0,
];
let input: Image = Image::try_create(4, 4, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (1500, 1500));
}
#[test]
fn test_10002_centered() {
// Arrange
let pixels: Vec<u8> = vec![
0, 0, 1, 0, 0,
1, 1, 0, 1, 1,
0, 0, 1, 0, 0,
];
let input: Image = Image::try_create(5, 3, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (2000, 1000));
}
#[test]
fn test_20000_corner() {
// Arrange
let pixels: Vec<u8> = vec![
0, 1, 1, 1,
1, 0, 0, 0,
1, 0, 0, 0,
1, 0, 0, 0,
];
let input: Image = Image::try_create(4, 4, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (1000, 1000));
}
#[test]
fn test_20001_corner() {
// Arrange
let pixels: Vec<u8> = vec![
0, 0, 0, 1,
0, 0, 0, 1,
0, 0, 0, 1,
1, 1, 1, 0,
];
let input: Image = Image::try_create(4, 4, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (2000, 2000));
}
#[test]
fn test_30000_odd_shapes() {
// Arrange
let pixels: Vec<u8> = vec![
0, 1, 1, 1, 1,
1, 0, 0, 0, 0,
];
let input: Image = Image::try_create(5, 2, pixels).expect("image");
// Act
let xy = input.center_of_mass(1000).expect("some");
// Assert
assert_eq!(xy, (2000, 200));
}
}
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