Glad to see this working completely client-side. I've been packing my own versions of libheif and libjxl using Wasm in a web application, and what got me was memory consumption on mobile Safari. Decoding a 48-megapixel picture to RGBA is ~190MB of memory usage prior to doing anything with it, and the page is killed by iOS far before you even approach the limits of wasm32. Do you pre-scale inputs if they're larger than a certain size when tracing?

The Certainty view is a nice touch. Is that edge band estimated from the source pixels, or by tracing a few slightly different versions of the image? I'm curious how it behaves on JPEG halos around a logo.