Alpha Desk

Colour and alpha can be stored multiplied together or not, almost nothing in a file says which, and reading one as the other puts a halo round every soft edge. The two mistakes have different signs, are worst at opposite ends of the same edge, and only one of them can leave the legal range - so a screenshot names the bug. Exact per-coverage errors, what unpremultiplying costs, what a matte colour bakes in, and what one bit of alpha destroys.

Every public app is built from a security-scanned skill and must pass a clean scan — skill and frontend — before it can be listed. Have a skill of your own? Turn it into an app — or read the step-by-step walkthrough.