Add `ImmutablePixelIterator` and `MutablePixelIterator` about image HOT 4 CLOSED

Perhaps add a Pixel type which could mutate the pixel by using mutable borrowed pointers internally.

from image.

Yes. First we have to agree on how the Pixel API should look like. I'm not sure how to do it most elegant. Rust does not allow values in generics and does not support higher-order types which makes it a bit messy supporting n-bits/channel and different color channels at the same time.

from image.

If we had a Pixel trait then we could add a generic parameter to the iterator.

Image format would then have a .iter() and .iter_mut() which returned a pixel iterator.

The user reads or sets values in the same way by using the Pixel trait.

from image.

I think this has been does already.

from image.