Image api improvements

[hydra]

While working with the img API I was frustrated to find that I had to create a vector of u8's even though I already had either a DynamicImage instance or PathBuf instance. e.g. when creating a new file (DynamicImage) or opening a file (PathBuf).

I also noted that img_dynamic visibility is pub(crate) which meant I could not use that either.

This PR adds three well-named methods (commit 1) and deprecates the old one (commit 2).

See commits/changes.

[charlescgs]

Hello, any particular reason this PR cannot be merged?

[jrmoulton]

@charlescgs

Hello, any particular reason this PR cannot be merged?

It hasn't passed CI and typically won't be reviewed until it does.

I do think though that we don't want to deprecate the img function. I think we can leave it as it is and just add the two new functions. Final approval is from dzhou121 though.

[panekj]

I do think though that we don't want to deprecate the img function

I agree, img is nice and convenient shorthand

[charlescgs]

@panekj then how about this:

pub fn img(image: impl Fn() -> Vec<u8> + 'static) -> Img {
    let image = image::load_from_memory(&image()).ok();
    let width = image.as_ref().map_or(0, |img| img.width());
    let height = image.as_ref().map_or(0, |img| img.height());
    let data = Arc::new(image.map_or(Default::default(), |img| img.into_rgba8().into_vec()));
    let blob = Blob::new(data);
    let image = peniko::Image::new(blob, peniko::Format::Rgba8, width, height);
    img_dynamic(move || image.clone())
}

pub fn img_from_path(image: impl Fn() -> PathBuf + 'static) -> Img {
    let image = image::open(&image()).ok();
    let width = image.as_ref().map_or(0, |img| img.width());
    let height = image.as_ref().map_or(0, |img| img.height());
    let data = Arc::new(image.map_or(Default::default(), |img| img.into_rgba8().into_vec()));
    let blob = Blob::new(data);
    let image = peniko::Image::new(blob, peniko::Format::Rgba8, width, height);
    img_dynamic(move || image.clone())
}

pub fn img_from_image(image: impl Fn() -> peniko::Image + 'static) -> Img {
    img_dynamic(move || image())
}