More than once, I’ve been stuck having to use images where a logo and/or some type is flattened onto a white background. The goal is to achieve something similar to the “Multiply” layer blending mode, but be able to save a PNG with a completely transparent background and no nasty, pixelated artifacts. About a year ago, I found a perfect Quartz-based app (or plugin, I forget which) that could remove the solid background from an image while preserving reflections, drop shadows, and the subtle parts of an image that have more complicated opacity. Unfortunately, I never bookmarked the author’s site nor did I write a blog post or a Tweet or anything that would have been useful.
After hours of searching for said app, I stumbled upon Mikeal Simburger’s KillWhite, a Photoshop plugin (and 64-bit PixelBender plugin!) that does the same thing. And what a relief. It works just as well as the mysterious app I first used, and even better is that Mikeal is working on a version that will key out a selected color.