When you need full color, but don’t need transparency, use JPEG instead.
implies that pixel-perfect results (non-lossy compression) is never desirable for images with full color, which I find to be a very provocative simplification.
On the other hand, on the web in general, perhaps it is good advice as a "rule of thumb" for people who aren't likely to deal with images where each pixel really matters.
There are actually two lossless JPEG modes even ignoring JPEG-2000: JPEG-LS and LJPEG. I don't know how widespread support for either is, but ffmpeg can encode to both. It confused the crap out of me a few months ago when I was trying to fix a bug and realized that the two were actually totally different formats.
The latter seems to be older and part of the original spec, while the former seems to be newer and a lot less bad.
Did he mean it literally, or just that you can fiddle with compression until you don't notice any artefacts? At that point, it's as good as lossless for most uses, IMHO.
When saving and closing an image, only to realize you need need to change something, thus necessitating a second save, which compounds loss. Granted, if you keep a lossless file around to edit, your problem is gone. But does everyone really do that with every file?
That's the only one I could imagine encountering, and if I've not saved the original, serves me right AFAIC.
But then, if I save the second with a higher-than-otherwise-optimal setting, then I can reduce the compounding of effects. It's cost me filesize to limit loss to the imperceptible, but it's still possible.
When you need full color, but don’t need transparency, use JPEG instead.
implies that pixel-perfect results (non-lossy compression) is never desirable for images with full color, which I find to be a very provocative simplification.
On the other hand, on the web in general, perhaps it is good advice as a "rule of thumb" for people who aren't likely to deal with images where each pixel really matters.