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use imgref::Img;
use imgref::ImgRef;
use rgb::ComponentMap;
use rgb::RGB;
use rgb::RGBA8;
#[inline]
fn weighed_pixel(px: RGBA8) -> (u16, RGB<u32>) {
if px.a == 0 {
return (0, RGB::new(0,0,0))
}
let weight = 256 - px.a as u16;
(weight, RGB::new(
px.r as u32 * weight as u32,
px.g as u32 * weight as u32,
px.b as u32 * weight as u32))
}
pub fn cleared_alpha(mut img: Img<Vec<RGBA8>>) -> Img<Vec<RGBA8>> {
let mut sum = RGB::new(0, 0, 0);
let mut weights = 0;
loop9::loop9_img(img.as_ref(), |_, _, top, mid, bot| {
if mid.curr.a == 255 || mid.curr.a == 0 {
return;
}
if chain(&top, &mid, &bot).any(|px| px.a == 0) {
let (w, px) = weighed_pixel(mid.curr);
weights += w as u64;
sum += px.map(|c| c as u64);
}
});
if weights == 0 {
return img;
}
let neutral_alpha = RGBA8::new((sum.r / weights) as u8, (sum.g / weights) as u8, (sum.b / weights) as u8, 0);
img.pixels_mut().filter(|px| px.a == 0).for_each(|px| *px = neutral_alpha);
let img2 = bleed_opaque_color(img.as_ref());
drop(img);
blur_transparent_pixels(img2.as_ref())
}
fn bleed_opaque_color(img: ImgRef<RGBA8>) -> Img<Vec<RGBA8>> {
let mut out = Vec::with_capacity(img.width() * img.height());
loop9::loop9_img(img, |_, _, top, mid, bot| {
out.push(if mid.curr.a == 255 {
mid.curr
} else {
let (weights, sum) = chain(&top, &mid, &bot)
.map(|c| weighed_pixel(*c))
.fold((0u32, RGB::new(0,0,0)), |mut sum, item| {
sum.0 += item.0 as u32;
sum.1 += item.1;
sum
});
if weights != 0 {
let mut avg = sum.map(|c| (c / weights) as u8);
if mid.curr.a == 0 {
avg.alpha(0)
} else {
avg.r = clamp(avg.r, premultiplied_minmax(mid.curr.r, mid.curr.a));
avg.g = clamp(avg.g, premultiplied_minmax(mid.curr.g, mid.curr.a));
avg.b = clamp(avg.b, premultiplied_minmax(mid.curr.b, mid.curr.a));
avg.alpha(mid.curr.a)
}
} else {
mid.curr
}
});
});
Img::new(out, img.width(), img.height())
}
fn blur_transparent_pixels(img: ImgRef<RGBA8>) -> Img<Vec<RGBA8>> {
let mut out = Vec::with_capacity(img.width() * img.height());
loop9::loop9_img(img, |_, _, top, mid, bot| {
out.push(if mid.curr.a == 255 {
mid.curr
} else {
let sum: RGB<u16> =
chain(&top, &mid, &bot).map(|px| px.rgb().map(|c| c as u16)).sum();
let mut avg = sum.map(|c| (c / 9) as u8);
if mid.curr.a == 0 {
avg.alpha(0)
} else {
avg.r = clamp(avg.r, premultiplied_minmax(mid.curr.r, mid.curr.a));
avg.g = clamp(avg.g, premultiplied_minmax(mid.curr.g, mid.curr.a));
avg.b = clamp(avg.b, premultiplied_minmax(mid.curr.b, mid.curr.a));
avg.alpha(mid.curr.a)
}
});
});
Img::new(out, img.width(), img.height())
}
#[inline(always)]
fn chain<'a, T>(top: &'a loop9::Triple<T>, mid: &'a loop9::Triple<T>, bot: &'a loop9::Triple<T>) -> impl Iterator<Item = &'a T> + 'a {
top.iter().chain(mid.iter()).chain(bot.iter())
}
#[inline]
fn clamp(px: u8, (min, max): (u8, u8)) -> u8 {
px.max(min).min(max)
}
#[inline]
fn premultiplied_minmax(px: u8, alpha: u8) -> (u8, u8) {
let alpha = alpha as u16;
let rounded = (px as u16) * alpha / 255 * 255;
let low = ((rounded + 16) / alpha) as u8;
let hi = ((rounded + 239) / alpha) as u8;
(low.min(px), hi.max(px))
}
#[test]
fn preminmax() {
assert_eq!((100,100), premultiplied_minmax(100, 255));
assert_eq!((78,100), premultiplied_minmax(100, 10));
assert_eq!(100*10/255, 78*10/255);
assert_eq!(100*10/255, 100*10/255);
assert_eq!((8,119), premultiplied_minmax(100, 2));
assert_eq!((16,239), premultiplied_minmax(100, 1));
assert_eq!((15,255), premultiplied_minmax(255, 1));
}