message: Changed `PixelsMut` to use `ChunksExactMut`
  This is to allow auto-vectorization to happen when calling `from_pixel` as well as other methods.
diff: @@ -3,7 +3,7 @@ use num_traits::Zero;
  use std::marker::PhantomData;
  use std::ops::{Deref, DerefMut, Index, IndexMut, Range};
  use std::path::Path;
  -use std::slice::{Chunks, ChunksMut};
  +use std::slice::{Chunks, ChunksMut, ChunksExact, ChunksExactMut};
  use crate::color::{FromColor, Luma, LumaA, Rgb, Rgba, Bgr, Bgra};
  use crate::flat::{FlatSamples, SampleLayout};
  @@ -20,7 +20,7 @@ pub struct Pixels<'a, P: Pixel + 'a>
  where
  P::Subpixel: 'a,
  {
  - chunks: Chunks<'a, P::Subpixel>,
  + chunks: ChunksExact<'a, P::Subpixel>,
  }
  impl<'a, P: Pixel + 'a> Iterator for Pixels<'a, P>
  @@ -59,7 +59,7 @@ pub struct PixelsMut<'a, P: Pixel + 'a>
  where
  P::Subpixel: 'a,
  {
  - chunks: ChunksMut<'a, P::Subpixel>,
  + chunks: ChunksExactMut<'a, P::Subpixel>,
  }
  impl<'a, P: Pixel + 'a> Iterator for PixelsMut<'a, P>
  @@ -140,7 +140,7 @@ where
  let row = self.pixels.next()?;
  Some(Pixels {
  // Note: this is not reached when CHANNEL_COUNT is 0.
  - chunks: row.chunks(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: row.chunks_exact(<P as Pixel>::CHANNEL_COUNT as usize),
  })
  }
  }
  @@ -163,7 +163,7 @@ where
  let row = self.pixels.next_back()?;
  Some(Pixels {
  // Note: this is not reached when CHANNEL_COUNT is 0.
  - chunks: row.chunks(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: row.chunks_exact(<P as Pixel>::CHANNEL_COUNT as usize),
  })
  }
  }
  @@ -212,7 +212,7 @@ where
  let row = self.pixels.next()?;
  Some(PixelsMut {
  // Note: this is not reached when CHANNEL_COUNT is 0.
  - chunks: row.chunks_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: row.chunks_exact_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  })
  }
  }
  @@ -235,7 +235,7 @@ where
  let row = self.pixels.next_back()?;
  Some(PixelsMut {
  // Note: this is not reached when CHANNEL_COUNT is 0.
  - chunks: row.chunks_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: row.chunks_exact_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  })
  }
  }
  @@ -538,7 +538,7 @@ where
  /// The iteration order is x = 0 to width then y = 0 to height
  pub fn pixels(&self) -> Pixels<P> {
  Pixels {
  - chunks: self.inner_pixels().chunks(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: self.inner_pixels().chunks_exact(<P as Pixel>::CHANNEL_COUNT as usize),
  }
  }
  @@ -688,7 +688,7 @@ where
  /// Returns an iterator over the mutable pixels of this image.
  pub fn pixels_mut(&mut self) -> PixelsMut<P> {
  PixelsMut {
  - chunks: self.inner_pixels_mut().chunks_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  + chunks: self.inner_pixels_mut().chunks_exact_mut(<P as Pixel>::CHANNEL_COUNT as usize),
  }
  }
  