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.
No. Don't. JPEG is for photos (and rarely for gradients). For drawings, line art, cartoons, clip art, etc. use 24bit PNGs - they work just fine.
SVG(.gz) could be even more compact (and just as important, resolution independent), but alas we'll have to wait a bit before support in browsers is common.
I wonder if Photoshop has planned future support for paletted, 8-bit alpha channel PNGs?
Fireworks supports 8bit+a. I'm also working on modernised pngquant, which might give higher-quality results than Fireworks:
It's definitely not time to stop fussing over Photoshop; that's not going away anytime soon.
It depends on who you are. I have never in my life used Photoshop. So if it disappeared from the planet, my life would change in no way, except that The GIMP would have more contributors.
What is the benefit of using pngcrush in addition to optipng? I got exellent reults using optipng only.
Furthermore, depending on agressivity they may change some encoding property of the PNG and make them easier (or harder) to recompress via other compressors.
The benefit of using both is that it often allows you to squeeze a few extra percentage point of compression. Ideally you should test all combinations of compressors (presence and sequence) but that tends to be a bit expensive, especially when you involve PNGOut as it takes a pretty long time to run.
FWIW, I just tried the following on a screen capture:
* OptiPNG alone
* PNGCrush then OptiPNG
* OptiPNG then PNGCrush
* Squash (which runs a sequence of PNGrush, OptiPNG and AdvPNG, it can also run PNGOut but I didn't install it)
The source file was 250K, the files that went through OptiPNG, PNGCrush+OptiPNG and OptiPNG+PNGCrush were compressed to 159K (with a slight edge for the one compressed via PNGCrush first: both Optis are 162997 bytes, while PNGCrush + OptiPNG is 162978) and the file compressed via PNGSquash is 144K (147249 bytes).
On some images each step cuts the file size by 10-15%.
Change the order and you'll get worse results.
Also pngout (and optipng) will convert 24bit PNGs to paletized PNGs if there are not a lot of colors. The often makes the file smaller - but not always. So I also suggest using the -c4 -c2 or -c6 options to pngout (as appropriate for the file) and checking if the file got smaller. But sure to pass -nc to optipng in that case.
I roll with PNGSquash
I wish that ImageAlpha GUI was available for windows.
Here's an evil image that will look red (instead of blue) when ICC isn't working, and it's also easily ruined by invalid gamma: