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blur: boxes_for_gaussian changes

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This commit is contained in:
Simon Gardling 2025-03-31 15:40:58 -04:00
parent 9199791f51
commit 61f0408bad
Signed by: titaniumtown
GPG Key ID: 9AB28AC10ECE533D
1 changed files with 8 additions and 9 deletions
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17
src/blur.rs
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@ -30,18 +30,17 @@ impl Blur {
/// Approximate 1D Gaussian filter of standard deviation sigma with N box filter passes. Each element in the output array contains the radius of the box filter for the corresponding pass.
fn boxes_for_gaussian<const N: usize>(sigma: f32) -> [usize; N] {
let w_ideal = (12.0 * sigma * sigma / N as f32 + 1.0).sqrt();
let sigma_sq = sigma.powi(2);
let w_ideal = (12.0 * sigma_sq / N as f32 + 1.0).sqrt();
let mut w = w_ideal as usize;
w -= 1 - (w & 1);
let mut m = 0.25 * (N * (w + 3)) as f32;
m -= 3.0 * sigma * sigma / (w + 1) as f32;
let m = m.round() as usize;
let m = (0.25 * (N * (w + 3)) as f32 - 3.0 * sigma_sq / (w + 1) as f32).round() as usize;
let mut result = [0; N];
for (i, value) in result.iter_mut().enumerate() {
*value = (if i < m { w - 1 } else { w + 1 }) / 2;
}
result
(0..N)
.map(|i| (w + 1 - 2 * (i < m) as usize) / 2)
.collect::<Vec<_>>()
.try_into()
.unwrap()
}
/// Perform one pass of the 2D box filter of the given radius. The result will be written to the src slice, while the buf slice is used as a scratch space.