Get Alpha Channel from DynamicImage

[bobbens]

Hello, I'm writing some signed distance function code, and I want to use the alpha channel of the image to compute it. What's the most elegant way of getting only the alpha channel of an image?

Ideally I would want something like image.to_alpha8(), but that doesn't seem to exist. Trying to use luma_alpha8, but it's quite confusing to figure out how to get only the alpha channel from there.

[bobbens]

let mut alpha: Vec<_> = img.to_luma_alpha8().pixels().map(|p| p.0[1]).collect();

seems to work well enough.