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.
No you can't. You can use Lossless JPEG instead, but regular JPEG (or JPEG2000) is a lossy format period.
edit: as tspiteri points out, JPEG 2000 does have a lossless mode. My bad. JPEG still does not though.
The latter seems to be older and part of the original spec, while the former seems to be newer and a lot less bad.
And yes, LJPEG is the "complete crap" version which predates (and was blown away by) PNG, JPEG-LS is a second take on a lossless jpeg format.
You're right in practise (AFAIK, libjpeg still doesn't support this mode), but see http://en.wikipedia.org/wiki/Lossless_JPEG
> No you can't. You can use Lossless JPEG
It's not, and the size of the file blows up to insane levels.
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.