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extern crate image;
extern crate num;
use image::{
Rgb,
Primitive,
};
use num::FromPrimitive;
fn scale<T: Primitive + FromPrimitive>(start: T, end: T, f: f64) -> T {
let start : f64 = start.to_f64().unwrap();
let end : f64 = end.to_f64().unwrap();
let delta : f64 = end - start;
let res : f64 = start + delta * f;
FromPrimitive::from_f64(res).unwrap()
}
pub fn scale_rgb<T: Primitive + FromPrimitive>(start: &Rgb<T>, end: &Rgb<T>, f: f64) -> Result<Rgb<T>, &'static str> {
if f.is_nan() || f < 0.0_f64 || f > 1.0_f64 {
if start == end {
Ok(Rgb{
data: [
start.data[0],
start.data[1],
start.data[2],
]
})
} else {
Err("f is outside [0; 1]")
}
} else {
Ok(Rgb{
data: [
scale(start.data[0], end.data[0], f),
scale(start.data[1], end.data[1], f),
scale(start.data[2], end.data[2], f),
]
})
}
}
#[test]
fn test_scaling_rgb_u8() {
let white : Rgb<u8> = Rgb{ data: [255, 255, 255] };
let black : Rgb<u8> = Rgb{ data: [ 0, 0, 0] };
let orange : Rgb<u8> = Rgb{ data: [255, 127, 0] };
let turquoise : Rgb<u8> = Rgb{ data: [ 0, 127, 255] };
let r = scale_rgb(&white, &black, -0.5);
assert!(r.is_err());
let r = scale_rgb(&white, &black, 1.5);
assert!(r.is_err());
let r = scale_rgb(&white, &black, std::f64::INFINITY);
assert!(r.is_err());
let r = scale_rgb(&white, &black, std::f64::NAN);
assert!(r.is_err());
let r = scale_rgb(&white, &white, -0.5);
assert!(r.is_ok());
assert!(r.unwrap() == white);
let r = scale_rgb(&white, &white, 1.5);
assert!(r.is_ok());
assert!(r.unwrap() == white);
let r = scale_rgb(&white, &white, std::f64::INFINITY);
assert!(r.is_ok());
assert!(r.unwrap() == white);
let r = scale_rgb(&white, &white, std::f64::NAN);
assert!(r.is_ok());
assert!(r.unwrap() == white);
let r = scale_rgb(&white, &black, 0.5);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [127, 127, 127] };
let r = r.unwrap();
assert!(r == e);
let r = scale_rgb(&black, &white, 0.5);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [127, 127, 127] };
let r = r.unwrap();
assert!(r == e);
let r = scale_rgb(&orange, &orange, 0.5);
assert!(r.is_ok());
let r = r.unwrap();
assert!(r == orange);
let r = scale_rgb(&orange, &orange, 0.0);
assert!(r.is_ok());
let r = r.unwrap();
assert!(r == orange);
let r = scale_rgb(&orange, &orange, 1.0);
assert!(r.is_ok());
let r = r.unwrap();
assert!(r == orange);
let r = scale_rgb(&orange, &turquoise, 0.3);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [178, 127, 76] };
let r = r.unwrap();
assert!(r == e);
let r = scale_rgb(&orange, &turquoise, 0.8);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [ 51, 127, 204] };
let r = r.unwrap();
assert!(r == e);
let r = scale_rgb(&turquoise, &orange, 0.3);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [ 76, 127, 178] };
let r = r.unwrap();
assert!(r == e);
let r = scale_rgb(&turquoise, &orange, 0.8);
assert!(r.is_ok());
let e : Rgb<u8> = Rgb{ data: [204, 127, 51] };
let r = r.unwrap();
assert!(r == e);
}