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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
use crate::error::Result;
use crate::image::Image;
use num_traits::abs;
#[allow(clippy::excessive_precision)]
const W_SIDE: f32 = 0.20345139757231578;
#[allow(clippy::excessive_precision)]
const W_CORNER: f32 = 0.0334829185968739;
const W_CENTER: f32 = 1.0 - 4.0 * (W_SIDE + W_CORNER);
fn compute_pixel_channel(
dc_factor: f32,
gap: f32,
x: usize,
row_top: &[f32],
row: &[f32],
row_bottom: &[f32],
) -> (f32, f32, f32) {
let tl = row_top[x - 1];
let tc = row_top[x];
let tr = row_top[x + 1];
let ml = row[x - 1];
let mc = row[x];
let mr = row[x + 1];
let bl = row_bottom[x - 1];
let bc = row_bottom[x];
let br = row_bottom[x + 1];
let corner = tl + tr + bl + br;
let side = ml + mr + tc + bc;
let sm = corner * W_CORNER + side * W_SIDE + mc * W_CENTER;
(mc, sm, gap.max(abs((mc - sm) / dc_factor)))
}
pub fn adaptive_lf_smoothing(lf_factors: [f32; 3], lf_image: &mut [Image<f32>; 3]) -> Result<()> {
let xsize = lf_image[0].size().0;
let ysize = lf_image[0].size().1;
if ysize <= 2 || xsize <= 2 {
return Ok(());
}
let mut smoothed: [Image<f32>; 3] = [
Image::<f32>::new((xsize, ysize))?,
Image::<f32>::new((xsize, ysize))?,
Image::<f32>::new((xsize, ysize))?,
];
for c in 0..3 {
for y in [0, ysize - 1] {
smoothed[c].row_mut(y).copy_from_slice(lf_image[c].row(y));
}
}
for y in 1..ysize - 1 {
for x in [0, xsize - 1] {
for c in 0..3 {
smoothed[c].row_mut(y)[x] = lf_image[c].row(y)[x];
}
}
for x in 1..xsize - 1 {
let gap = 0.5;
let (mc_x, sm_x, gap) = compute_pixel_channel(
lf_factors[0],
gap,
x,
lf_image[0].row(y - 1),
lf_image[0].row(y),
lf_image[0].row(y + 1),
);
let (mc_y, sm_y, gap) = compute_pixel_channel(
lf_factors[1],
gap,
x,
lf_image[1].row(y - 1),
lf_image[1].row(y),
lf_image[1].row(y + 1),
);
let (mc_b, sm_b, gap) = compute_pixel_channel(
lf_factors[2],
gap,
x,
lf_image[2].row(y - 1),
lf_image[2].row(y),
lf_image[2].row(y + 1),
);
let factor = (3.0 - 4.0 * gap).max(0.0);
smoothed[0].row_mut(y)[x] = (sm_x - mc_x) * factor + mc_x;
smoothed[1].row_mut(y)[x] = (sm_y - mc_y) * factor + mc_y;
smoothed[2].row_mut(y)[x] = (sm_b - mc_b) * factor + mc_b;
}
}
*lf_image = smoothed;
Ok(())
}