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Implement Box blur fast filter that could approximate gaussian filter #223

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@light-le light-le commented Jan 16, 2025

solve #168. The algorithm was derived from this blog post

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can you add benchmarks to it as well?

@light-le
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You mean in crates/kornia-imgproc/benches/bench_filters.rs ? Sure ok

@@ -61,6 +61,36 @@ pub fn sobel_kernel_1d(kernel_size: usize) -> (Vec<f32>, Vec<f32>) {
(kernel_x, kernel_y)
}


/// Create list of optimized box blur kernels based on gaussian sigma
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Suggested change
/// Create list of optimized box blur kernels based on gaussian sigma
/// Create list of optimized box blur kernels based on gaussian sigma
///

/// # Arguments
///
/// * `sigma` = The sigma of the gaussian kernel
/// * `kernels` = The number of times the box blur kernels would be applied, ideally from 3-5
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/// * `kernels` = The number of times the box blur kernels would be applied, ideally from 3-5
/// * `kernels` = The number of times the box blur kernels would be applied, ideally from 3-5
///

@@ -92,4 +122,11 @@ mod tests {
assert_eq!(k, expected[i]);
}
}

#[test]
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Maybe add also some test that it’s not only ones ?

/// * `src` - The source image with shape (H, W, C).
/// * `dst` - The destination image with shape (H, W, C).
/// * `kernel_size` - The size of the kernel (kernel_x, kernel_y).
/// * `sigma` - The sigma of the gaussian kernel.
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Specify that it should be x-y ordered

mod tests {
use super::*;

#[test]
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I would some simple numbers test too similar to the other functions to verify that’s doing the right thing

@@ -88,6 +88,72 @@ pub fn separable_filter<const C: usize>(
Ok(())
}


/// Apply a fast filter horizontally, take advantage of property where all
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Split header docs. Usually there’s a single line explaining in short the purpose of the function followed by end of line then you can add some clarification, formulation of anything needed

/// * `src` - The source image with shape (H, W, C).
/// * `dst_transposed` - The destination image with shape (W, H, C).
/// * `half_kernel_x_size` - Half of the kernel at weight 1. The total size would be 2*this+1
pub fn fast_horizontal_filter<const C: usize>(
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pub fn fast_horizontal_filter<const C: usize>(
fn fast_horizontal_filter<const C: usize>(

I wouldn’t make public to users, this is more a utility function

/// * `half_kernel_x_size` - Half of the kernel at weight 1. The total size would be 2*this+1
pub fn fast_horizontal_filter<const C: usize>(
src: &Image<f32, C>,
dst_transposed: &mut Image<f32, C>,
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For consistency just dst ?

row_acc[ch] += src_data[kernel_pix_offset];
}
leftmost_pixel[ch] = *source_pixel;
rightmost_pixel[ch] = src_data[pix_offset+((src.cols()-1)*C)];
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(src.cols()-1)*C) could be computed outside before the loops


if c == 0 {
row_acc[ch] = *source_pixel * (half_kernel_x_size+1) as f32;
let mut kernel_pix_offset = pix_offset;
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Wondering wether this offset could be precomputed beforehand as you are computing several times in the top level function

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@johnnv1 any idea why python tests are failing (I believe it’s unrelated to this PR). Shouldn’t we be using the new just commands in https://github.com/kornia/kornia-rs/blob/main/.github/workflows/python_test.yml#L40

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johnnv1 commented Jan 19, 2025

@johnnv1 any idea why python tests are failing (I believe it’s unrelated to this PR). Shouldn’t we be using the new just commands in https://github.com/kornia/kornia-rs/blob/main/.github/workflows/python_test.yml#L40

yeah, seems unrelated, but should be working

@johnnv1 johnnv1 closed this Jan 21, 2025
@johnnv1 johnnv1 reopened this Jan 21, 2025
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3 participants