Really nice writeup, especially the part about the semi-transparency issue and needing pixel normalization after the pipeline output. That’s the kind of edge case that never shows up until you actually ship something real.
I’ve been building something in a similar spirit, a browser-based creative tool called PaperAnimators, built with plain JavaScript, HTML, and CSS, no frameworks, everything running client-side so nothing ever touches a server. It turns photos into paper-style animated designs, and one of the tools in the suite uses AI-based background removal too, so I hit a lot of the same “why is my output slightly wrong” moments you’re describing.
What stood out to me in your post is how clean the Pipeline API made this. I’ve mostly hand-rolled canvas-based image processing so far, so seeing RMBG-1.4 handled through Transformers.js with just a few lines is making me rethink part of my own background removal flow. Curious whether you’re planning to keep expanding this into a full editor, or keep it focused on one task done really well? Either direction seems solid.