Add height/width swap for SharedPixelBuffer

[guimath]

Hi I'm writing an image gallery where the images are the same size but sometimes in landscape, sometimes in portrait.

Basically the idea is to only create a SharedPixelBuffer at the initialization and then directly change the data depending on the image to display. The issue is when the orientation changes, AFAIK I then have to re create a SharedPixelBuffer, even though the data size has not changed.

A work around I have tested is adding a swap_width_height function to SharedPixelBuffer like so :

impl<Pixel> SharedPixelBuffer<Pixel> {
    ...
    /// swaps width and height without changing the data
    pub fn swap_width_height(&mut self) {
        std::mem::swap(&mut self.width, &mut self.height);
    }
}

Was wondering if such a function would be a good addition or if there's another way of going about it.

[tronical]

I'm not sure that function would be a good fit, but perhaps we could add a these two functions like in the image crate: https://docs.rs/image/latest/image/struct.ImageBuffer.html#method.from_vec (but shared_vector in the name).

@ogoffart what do you think?