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Merge pull request #2302 from torfmaster/feature/fast-blur
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Fast Blur
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HeroicKatora authored Oct 11, 2024
2 parents a373218 + e5672ff commit d4a0d26
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Showing 9 changed files with 302 additions and 3 deletions.
10 changes: 10 additions & 0 deletions Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -105,3 +105,13 @@ harness = false
[[bench]]
name = "copy_from"
harness = false

[[bench]]
path = "benches/fast_blur.rs"
name = "fast_blur"
harness = false

[[bench]]
path = "benches/blur.rs"
name = "blur"
harness = false
13 changes: 13 additions & 0 deletions benches/blur.rs
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@@ -0,0 +1,13 @@
use criterion::{criterion_group, criterion_main, Criterion};
use image::{imageops::blur, ImageBuffer, Rgb};

pub fn bench_fast_blur(c: &mut Criterion) {
let src = ImageBuffer::from_pixel(1024, 768, Rgb([255u8, 0, 0]));

c.bench_function("blur", |b| {
b.iter(|| blur(&src, 50.0));
});
}

criterion_group!(benches, bench_fast_blur);
criterion_main!(benches);
13 changes: 13 additions & 0 deletions benches/fast_blur.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
use criterion::{criterion_group, criterion_main, Criterion};
use image::{imageops::fast_blur, ImageBuffer, Rgb};

pub fn bench_fast_blur(c: &mut Criterion) {
let src = ImageBuffer::from_pixel(1024, 768, Rgb([255u8, 0, 0]));

c.bench_function("fast_blur", |b| {
b.iter(|| fast_blur(&src, 50.0));
});
}

criterion_group!(benches, bench_fast_blur);
criterion_main!(benches);
2 changes: 2 additions & 0 deletions examples/fast_blur/.gitignore
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@@ -0,0 +1,2 @@
mandril_color_blurred.tif

14 changes: 14 additions & 0 deletions examples/fast_blur/main.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
use image::ImageReader;

fn main() {
let path = concat!(
env!("CARGO_MANIFEST_DIR"),
"/tests/images/tiff/testsuite/mandrill.tiff"
);
let img = ImageReader::open(path).unwrap().decode().unwrap();

let img2 = img.blur(10.0);

img2.save("examples/fast_blur/mandril_color_blurred.tif")
.unwrap();
}
10 changes: 10 additions & 0 deletions src/dynimage.rs
Original file line number Diff line number Diff line change
Expand Up @@ -824,11 +824,21 @@ impl DynamicImage {

/// Performs a Gaussian blur on this image.
/// `sigma` is a measure of how much to blur by.
/// Use [DynamicImage::fast_blur()] for a faster but less
/// accurate version.
#[must_use]
pub fn blur(&self, sigma: f32) -> DynamicImage {
dynamic_map!(*self, ref p => imageops::blur(p, sigma))
}

/// Performs a fast blur on this image.
/// `sigma` is the standard deviation of the
/// (approximated) Gaussian
#[must_use]
pub fn fast_blur(&self, sigma: f32) -> DynamicImage {
dynamic_map!(*self, ref p => imageops::fast_blur(p, sigma))
}

/// Performs an unsharpen mask on this image.
/// `sigma` is the amount to blur the image by.
/// `threshold` is a control of how much to sharpen.
Expand Down
152 changes: 152 additions & 0 deletions src/imageops/fast_blur.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,152 @@
use num_traits::clamp;

use crate::{ImageBuffer, Pixel, Primitive};

/// Approximation of Gaussian blur after
/// Kovesi, P.: Fast Almost-Gaussian Filtering The Australian Pattern
/// Recognition Society Conference: DICTA 2010. December 2010. Sydney.
pub fn fast_blur<P: Pixel>(
image_buffer: &ImageBuffer<P, Vec<P::Subpixel>>,
sigma: f32,
) -> ImageBuffer<P, Vec<P::Subpixel>> {
let (width, height) = image_buffer.dimensions();

if width == 0 || height == 0 {
return image_buffer.clone();
}
let mut samples = image_buffer.as_flat_samples().samples.to_vec();
let num_passes = 3;

let boxes = boxes_for_gauss(sigma, num_passes);

for radius in boxes.iter().take(num_passes) {
let horizontally_blurred_transposed = horizontal_fast_blur_half::<P::Subpixel>(
&samples,
width as usize,
height as usize,
(*radius - 1) / 2,
P::CHANNEL_COUNT as usize,
);
samples = horizontal_fast_blur_half::<P::Subpixel>(
&horizontally_blurred_transposed,
height as usize,
width as usize,
(*radius - 1) / 2,
P::CHANNEL_COUNT as usize,
);
}
ImageBuffer::from_raw(width, height, samples).unwrap()
}

fn boxes_for_gauss(sigma: f32, n: usize) -> Vec<usize> {
let w_ideal = f32::sqrt((12.0 * sigma.powi(2) / (n as f32)) + 1.0);
let mut w_l = w_ideal.floor();
if w_l % 2.0 == 0.0 {
w_l -= 1.0
};
let w_u = w_l + 2.0;

let m_ideal = 0.25 * (n as f32) * (w_l + 3.0) - 3.0 * sigma.powi(2) * (w_l + 1.0).recip();

let m = f32::round(m_ideal) as usize;

(0..n)
.map(|i| if i < m { w_l as usize } else { w_u as usize })
.collect::<Vec<_>>()
}

fn channel_idx(channel: usize, idx: usize, channel_num: usize) -> usize {
channel_num * idx + channel
}

fn horizontal_fast_blur_half<P: Primitive>(
samples: &[P],
width: usize,
height: usize,
r: usize,
channel_num: usize,
) -> Vec<P> {
let channel_size = width * height;

let mut out_samples = vec![P::from(0).unwrap(); channel_size * channel_num];
let mut vals = vec![0.0; channel_num];

let min_value = P::DEFAULT_MIN_VALUE.to_f32().unwrap();
let max_value = P::DEFAULT_MAX_VALUE.to_f32().unwrap();

for row in 0..height {
for (channel, value) in vals.iter_mut().enumerate().take(channel_num) {
*value = ((-(r as isize))..(r + 1) as isize)
.map(|x| {
extended_f(
samples,
width,
height,
x,
row as isize,
channel,
channel_num,
)
.to_f32()
.unwrap_or(0.0)
})
.sum()
}

for column in 0..width {
for (channel, channel_val) in vals.iter_mut().enumerate() {
let val = *channel_val / (2.0 * r as f32 + 1.0);
let val = clamp(val, min_value, max_value);
let val = P::from(val).unwrap();

let destination_row = column;
let destination_column = row;
let destination_sample_index = channel_idx(
channel,
destination_column + destination_row * height,
channel_num,
);
out_samples[destination_sample_index] = val;
*channel_val = *channel_val
- extended_f(
samples,
width,
height,
column as isize - r as isize,
row as isize,
channel,
channel_num,
)
.to_f32()
.unwrap_or(0.0)
+ extended_f(
samples,
width,
height,
{ column + r + 1 } as isize,
row as isize,
channel,
channel_num,
)
.to_f32()
.unwrap_or(0.0)
}
}
}

out_samples
}

fn extended_f<P: Primitive>(
samples: &[P],
width: usize,
height: usize,
x: isize,
y: isize,
channel: usize,
channel_num: usize,
) -> P {
let x = clamp(x, 0, width as isize - 1) as usize;
let y = clamp(y, 0, height as isize - 1) as usize;
samples[channel_idx(channel, y * width + x, channel_num)]
}
89 changes: 86 additions & 3 deletions src/imageops/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -31,8 +31,11 @@ mod affine;
// Public only because of Rust bug:
// https://github.com/rust-lang/rust/issues/18241
pub mod colorops;
mod fast_blur;
mod sample;

pub use fast_blur::fast_blur;

/// Return a mutable view into an image
/// The coordinates set the position of the top left corner of the crop.
pub fn crop<I: GenericImageView>(
Expand Down Expand Up @@ -353,9 +356,12 @@ where
#[cfg(test)]
mod tests {

use super::{overlay, overlay_bounds_ext};
use super::*;
use crate::color::Rgb;
use crate::GrayAlphaImage;
use crate::GrayImage;
use crate::ImageBuffer;
use crate::RgbImage;
use crate::RgbaImage;

#[test]
Expand Down Expand Up @@ -478,9 +484,86 @@ mod tests {
}

#[test]
/// Test blur doesn't panick when passed 0.0
/// Test blur doesn't panic when passed 0.0
fn test_blur_zero() {
let image = RgbaImage::new(50, 50);
let _ = super::blur(&image, 0.0);
let _ = blur(&image, 0.0);
}

#[test]
/// Test fast blur doesn't panic when passed 0.0
fn test_fast_blur_zero() {
let image = RgbaImage::new(50, 50);
let _ = fast_blur(&image, 0.0);
}

#[test]
/// Test fast blur doesn't panic when passed negative numbers
fn test_fast_blur_negative() {
let image = RgbaImage::new(50, 50);
let _ = fast_blur(&image, -1.0);
}

#[test]
/// Test fast blur doesn't panic when sigma produces boxes larger than the image
fn test_fast_large_sigma() {
let image = RgbaImage::new(1, 1);
let _ = fast_blur(&image, 50.0);
}

#[test]
/// Test blur doesn't panic when passed an empty image (any direction)
fn test_fast_blur_empty() {
let image = RgbaImage::new(0, 0);
let _ = fast_blur(&image, 1.0);
let image = RgbaImage::new(20, 0);
let _ = fast_blur(&image, 1.0);
let image = RgbaImage::new(0, 20);
let _ = fast_blur(&image, 1.0);
}

#[test]
/// Test fast blur works with 3 channels
fn test_fast_blur_3_channels() {
let image = RgbImage::new(50, 50);
let _ = fast_blur(&image, 1.0);
}

#[test]
/// Test fast blur works with 2 channels
fn test_fast_blur_2_channels() {
let image = GrayAlphaImage::new(50, 50);
let _ = fast_blur(&image, 1.0);
}

#[test]
/// Test fast blur works with 1 channel
fn test_fast_blur_1_channels() {
let image = GrayImage::new(50, 50);
let _ = fast_blur(&image, 1.0);
}

#[test]
#[cfg(feature = "tiff")]
fn fast_blur_approximates_gaussian_blur_well() {
let path = concat!(
env!("CARGO_MANIFEST_DIR"),
"/tests/images/tiff/testsuite/rgb-3c-16b.tiff"
);
let image = crate::open(path).unwrap();
let image_blurred_gauss = image.blur(50.0).to_rgb8();
let image_blurred_gauss_samples = image_blurred_gauss.as_flat_samples();
let image_blurred_gauss_bytes = image_blurred_gauss_samples.as_slice();
let image_blurred_fast = image.fast_blur(50.0).to_rgb8();
let image_blurred_fast_samples = image_blurred_fast.as_flat_samples();
let image_blurred_fast_bytes = image_blurred_fast_samples.as_slice();

let error = image_blurred_gauss_bytes
.iter()
.zip(image_blurred_fast_bytes.iter())
.map(|(a, b)| ((*a as f32 - *b as f32) / (*a as f32)))
.sum::<f32>()
/ (image_blurred_gauss_bytes.len() as f32);
assert!(error < 0.05);
}
}
2 changes: 2 additions & 0 deletions src/imageops/sample.rs
Original file line number Diff line number Diff line change
Expand Up @@ -953,6 +953,8 @@ where

/// Performs a Gaussian blur on the supplied image.
/// ```sigma``` is a measure of how much to blur by.
/// Use [crate::imageops::fast_blur()] for a faster but less
/// accurate version.
pub fn blur<I: GenericImageView>(
image: &I,
sigma: f32,
Expand Down

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