pub fn rotate180<P>(image: &Image<P>) -> Image<P>
where
    P: Pixel,
{
    let mut out = image.clone();
    rotate180_mut(&mut out);
    out
}
Rotates an image 180 degrees clockwise.

# Examples
```
use imageproc::geometric_transformations::rotate180;
use imageproc::gray_image;

let image = gray_image!(
1, 2, 0, 0;
3, 4, 0, 0;
0, 0, 0, 0;
0, 0, 0, 0);

let rotated = rotate180(&image);

assert_eq!(rotated, gray_image!(
0, 0, 0, 0;
0, 0, 0, 0;
0, 0, 4, 3;
0, 0, 2, 1));
```
src/geometric_transformations.rs