Running this now...

  Build transparent-png.html - a tool that lets you open any image and then click on colors within that image to make them transparent - showing a preview of the resulting PNG against a checkerboard pattern and optional against other selected background colors below, plus a download PNG option
  
  It should also accept pasted images

Here's what I got (from Opus 4.5 in Claude Code for web via the Claude iPhone app): https://tools.simonwillison.net/transparent-png

▲ eliben 12 hours ago | parent | next [-]

Nice, I'm proud I managed to nerd-snipe you :-) Thanks for taking the time.

Seriously, though, I think this solves a nicely framed simpler problem. I was thinking about a more general tool, but that's genuinely hard (you'll need heavy CV algorithms or a special ML model to detect what is background what what isn't).

To be honest, what you built here is probably sufficient anyway, because the models are better at obeying "create a white background" or "create a 0xffffff background" than "transparent", so this tool can post-process to what's needed.

When asked for "transparent", I've had a model generate a fake checkerboard pattern of gray colors to imitate how viewers render transparent areas :-) For this kind of nonsense, the transparent-png tool wouldn't do!

	▲	singpolyma3 8 hours ago \| parent [-]
		The best thing to say to an image model IME is "use a colour/chroma key background" and then it gives you green or blue or whatever depending on colours used in the image.

▲ indigodaddy 13 hours ago | parent | prev [-]

Dude, you are amazing. Maybe you should make a suggestion box. Then while you are sleeping, the AI could evaluate the suggestions, and if they are good, it could prototype the tool, and then you could review the prototypes in your waking hours before clicking the tool to production. :)

(I’m not actually kidding)