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Optimize horizontal filter to iterate over chucks of the input slice.

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This commit is contained in:
mindv0rtex 2021-02-24 23:39:13 -05:00
parent b88eebc4f8
commit 6966433c9c
1 changed files with 13 additions and 22 deletions
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35
src/blur.rs
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@ -44,37 +44,28 @@ fn box_blur(
radius: usize,
decay: f32,
) {
box_blur_h(src, buf, width, height, radius, 1.0);
box_blur_h(src, buf, width, radius);
box_blur_v(buf, src, width, height, radius, decay);
}
/// Perform one pass of the 1D box filter of the given radius along x axis. Applies the decay factor
/// to the destination buffer.
fn box_blur_h(
src: &[f32],
dst: &mut [f32],
width: usize,
height: usize,
radius: usize,
decay: f32,
) {
let weight = decay / (2 * radius + 1) as f32;
/// Perform one pass of the 1D box filter of the given radius along x axis.
fn box_blur_h(src: &[f32], dst: &mut [f32], width: usize, radius: usize) {
let weight = 1.0 / (2 * radius + 1) as f32;
// TODO: Parallelize with rayon
for i in 0..height {
for (src_row, dst_row) in src.chunks_exact(width).zip(dst.chunks_exact_mut(width)) {
// First we build a value for the beginning of each row. We assume periodic boundary
// conditions, so we need to push the left index to the opposite side of the row.
let mut value = src[(i + 1) * width - radius - 1];
let mut value = src_row[width - radius - 1];
for j in 0..radius {
value += src[(i + 1) * width - radius + j] + src[i * width + j];
value += src_row[width - radius + j] + src_row[j];
}
// At this point "value" contains the unweighted sum for the right-most row element.
for current_id in i * width..(i + 1) * width {
let left_id = ((current_id + width - radius - 1) & (width - 1)) + i * width;
let right_id = ((current_id + radius) & (width - 1)) + i * width;
value += src[right_id] - src[left_id];
dst[current_id] = value * weight;
for current_id in 0..width {
let left_id = (current_id + width - radius - 1) & (width - 1);
let right_id = (current_id + radius) & (width - 1);
value += src_row[right_id] - src_row[left_id];
dst_row[current_id] = value * weight;
}
}
}
@ -118,7 +109,7 @@ mod tests {
fn test_blur() {
let src = vec![1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0];
let mut dst = vec![0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
box_blur_v(&src, &mut dst, 2, 4, 1, 1.0);
box_blur_h(&src, &mut dst, 4, 1);
println!("Out: {:?}", dst);
}
}