use crate::{ImageRef, ImageRefMut, FuzzyZero, RGBA8, f64_bound};
pub fn arithmetic_composite(
k1: f64,
k2: f64,
k3: f64,
k4: f64,
src1: ImageRef,
src2: ImageRef,
dest: ImageRefMut,
) {
assert!(src1.width == src2.width && src1.width == dest.width);
assert!(src1.height == src2.height && src1.height == dest.height);
let calc = |i1, i2, max| {
let i1 = i1 as f64 / 255.0;
let i2 = i2 as f64 / 255.0;
let result = k1 * i1 * i2 + k2 * i1 + k3 * i2 + k4;
f64_bound(0.0, result, max)
};
let mut i = 0;
for (c1, c2) in src1.data.iter().zip(src2.data.iter()) {
let a = calc(c1.a, c2.a, 1.0);
if a.is_fuzzy_zero() {
i += 1;
continue;
}
let r = (calc(c1.r, c2.r, a) * 255.0) as u8;
let g = (calc(c1.g, c2.g, a) * 255.0) as u8;
let b = (calc(c1.b, c2.b, a) * 255.0) as u8;
let a = (a * 255.0) as u8;
dest.data[i] = RGBA8 { r, g, b, a };
i += 1;
}
}