ndarray-vision 0.3.0

A computer vision library built on top of ndarray
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use crate::core::*;
use crate::processing::*;
use core::mem::MaybeUninit;
use core::ops::Neg;
use ndarray::{prelude::*, s, DataMut, OwnedRepr, Zip};
use num_traits::{cast::FromPrimitive, real::Real, Num, NumAssignOps};
use std::marker::Sized;

/// Runs the sobel operator on an image
pub trait SobelExt
where
    Self: Sized,
{
    /// Type to output
    type Output;
    /// Returns the magnitude output of the sobel - an image of only lines
    fn apply_sobel(&self) -> Result<Self::Output, Error>;

    /// Returns the magntitude and rotation outputs for use in other algorithms
    /// like the Canny edge detector. Rotation is in radians
    fn full_sobel(&self) -> Result<(Self::Output, Self::Output), Error>;
}

fn get_edge_images<T, U>(mat: &ArrayBase<U, Ix3>) -> Result<(Array3<T>, Array3<T>), Error>
where
    U: DataMut<Elem = T>,
    T: Copy + Clone + Num + NumAssignOps + Neg<Output = T> + FromPrimitive + Real,
{
    let v_temp: Array3<T> = SobelFilter::build_with_params(Orientation::Vertical).unwrap();
    let h_temp: Array3<T> = SobelFilter::build_with_params(Orientation::Horizontal).unwrap();
    let shape = (v_temp.shape()[0], v_temp.shape()[1], mat.shape()[2]);
    let mut h_kernel = Array3::<T>::uninit(shape);
    let mut v_kernel = Array3::<T>::uninit(shape);
    for i in 0..mat.dim().2 {
        h_temp
            .slice(s![.., .., 0])
            .assign_to(h_kernel.slice_mut(s![.., .., i]));
        v_temp
            .slice(s![.., .., 0])
            .assign_to(v_kernel.slice_mut(s![.., .., i]));
    }
    let h_kernel = unsafe { h_kernel.assume_init() };
    let v_kernel = unsafe { v_kernel.assume_init() };
    let h_deriv = mat.conv2d(h_kernel.view())?;
    let v_deriv = mat.conv2d(v_kernel.view())?;

    Ok((h_deriv, v_deriv))
}

impl<T, U> SobelExt for ArrayBase<U, Ix3>
where
    U: DataMut<Elem = T>,
    T: Copy + Clone + Num + NumAssignOps + Neg<Output = T> + FromPrimitive + Real,
{
    type Output = ArrayBase<OwnedRepr<T>, Ix3>;

    fn apply_sobel(&self) -> Result<Self::Output, Error> {
        let (h_deriv, v_deriv) = get_edge_images(self)?;
        let res_shape = h_deriv.dim();
        let mut result = Self::Output::uninit(res_shape);
        for r in 0..res_shape.0 {
            for c in 0..res_shape.1 {
                for channel in 0..res_shape.2 {
                    let temp = (h_deriv[[r, c, channel]].powi(2)
                        + v_deriv[[r, c, channel]].powi(2))
                    .sqrt();
                    unsafe {
                        *result.uget_mut([r, c, channel]) = MaybeUninit::new(temp);
                    }
                }
            }
        }
        Ok(unsafe { result.assume_init() })
    }

    fn full_sobel(&self) -> Result<(Self::Output, Self::Output), Error> {
        let (h_deriv, v_deriv) = get_edge_images(self)?;

        let mut magnitude = h_deriv.mapv(|x| x.powi(2)) + v_deriv.mapv(|x| x.powi(2));
        magnitude.mapv_inplace(|x| x.sqrt());

        let dim = h_deriv.dim();
        let mut rotation = Array3::uninit((dim.0, dim.1, dim.2));
        Zip::from(&mut rotation)
            .and(&h_deriv)
            .and(&v_deriv)
            .for_each(|r, &h, &v| *r = MaybeUninit::new(h.atan2(v)));

        let rotation = unsafe { rotation.assume_init() };

        Ok((magnitude, rotation))
    }
}

impl<T, U, C> SobelExt for ImageBase<U, C>
where
    U: DataMut<Elem = T>,
    T: Copy + Clone + Num + NumAssignOps + Neg<Output = T> + FromPrimitive + Real,
    C: ColourModel,
{
    type Output = Image<T, C>;

    fn apply_sobel(&self) -> Result<Self::Output, Error> {
        let data = self.data.apply_sobel()?;
        Ok(Image::from_data(data))
    }

    fn full_sobel(&self) -> Result<(Self::Output, Self::Output), Error> {
        self.data
            .full_sobel()
            .map(|(m, r)| (Image::from_data(m), Image::from_data(r)))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use approx::*;

    #[test]
    fn simple() {
        let mut image: Image<f64, Gray> = ImageBase::new(11, 11);
        image.data.slice_mut(s![4..7, 4..7, ..]).fill(1.0);
        image.data.slice_mut(s![3..8, 5, ..]).fill(1.0);
        image.data.slice_mut(s![5, 3..8, ..]).fill(1.0);

        let sobel = image.full_sobel().unwrap();

        // Did a calculation of sobel_mag[1..9, 1..9, ..] in a spreadsheet
        #[rustfmt::skip]
        let mag = vec![0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
            0.0, 0.0, 0.0, 1.41421356237301, 2.0, 1.41421356237301, 0.0, 0.0, 0.0,
            0.0, 0.0, 1.41421356237301, 4.24264068711929, 4.0, 4.24264068711929, 1.4142135623731, 0.0, 0.0, 
            0.0, 1.4142135623731, 4.24264068711929, 4.24264068711929, 2.0, 4.24264068711929, 4.24264068711929, 1.4142135623731, 0.0,
            0.0, 2.0, 4.0, 2.0, 0.0, 2.0, 4.0, 2.0, 0.0,
            0.0, 1.4142135623731, 4.24264068711929, 4.24264068711929, 2.0, 4.24264068711929, 4.24264068711929, 1.4142135623731, 0.0,
            0.0, 0.0, 1.4142135623731, 4.24264068711929, 4.0, 4.24264068711929, 1.4142135623731, 0.0,
            0.0, 0.0, 0.0, 0.0, 1.4142135623731, 2.0, 1.4142135623731, 0.0, 0.0,
            0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
        ];

        let mag = Array::from_shape_vec((9, 9), mag).unwrap();

        assert_abs_diff_eq!(sobel.0.data.slice(s![1..10, 1..10, 0]), mag, epsilon = 1e-5);

        let only_mag = image.apply_sobel().unwrap();
        assert_abs_diff_eq!(sobel.0.data, only_mag.data);

        // Did a calculation of sobel_rot[1..9, 1..9, ..] in a spreadsheet
        #[rustfmt::skip]
        let rot = vec![0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,
                       0.00000000000000,0.00000000000000,0.00000000000000,-2.35619449019234,3.14159265358979,2.35619449019234,0.00000000000000,0.00000000000000,0.00000000000000,
                       0.00000000000000,0.00000000000000,-2.35619449019234,-2.35619449019234,3.14159265358979,2.35619449019234,2.35619449019234,0.00000000000000,0.00000000000000,
                       0.00000000000000,-2.35619449019234,-2.35619449019234,-2.35619449019234,3.14159265358979,2.35619449019234,2.35619449019234,2.35619449019234,0.00000000000000,
                       0.00000000000000,-1.57079632679490,-1.57079632679490,-1.57079632679490,0.00000000000000,1.57079632679490,1.57079632679490,1.57079632679490,0.00000000000000,
                       0.00000000000000,-0.78539816339745,-0.78539816339745,-0.78539816339745,0.00000000000000,0.78539816339745,0.78539816339745,0.78539816339745,0.00000000000000,
                       0.00000000000000,0.00000000000000,-0.78539816339745,-0.78539816339745,0.00000000000000,0.78539816339745,0.78539816339745,0.00000000000000,0.00000000000000,
                       0.00000000000000,0.00000000000000,0.00000000000000,-0.78539816339745,0.00000000000000,0.78539816339745,0.00000000000000,0.00000000000000,0.00000000000000,
                       0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000,0.00000000000000];
        let rot = Array::from_shape_vec((9, 9), rot).unwrap();

        assert_abs_diff_eq!(sobel.1.data.slice(s![1..10, 1..10, 0]), rot, epsilon = 1e-5);
    }
}