In some cases PNG compresses better than JPG.
For example when skins have large areas of the same colors, without gradients, then PNG is better.
PNG Compression is loseless and sometimes skinfiles are already <400kb as png. When converting to JPG it is then nessecary to use lossy compression which lowers quality a bit.
So the option to upload png-files to LFSworld might be useful?

"In some cases" I think png skins would be better in every case.

Nope.

Quote from Gutholz :

So the option to upload png-files to LFSworld might be useful?

I don't think LFS can make use of png files at the moment, so png uploads (and in particular downloads) will not be possible. Unless I'd convert them to jpg on the server, but then what's the point of uploading in png in the first place
Just make sure you don't use too much compression on your jpg files. Imo the quality is totally acceptable then for this purpose.

The only place where I could immagine a practical advantage of png skins was, if the windows were skinable *cough* for example for something like this *cough*

Well it is not a huge issue to me.
But for example this skin for Raceabout:


As .png it is 114 kb
As .jpg with 100% qualy it is 433 kb
The jpg is 3.7 times larger.
(Not a big problem: saved with 98% or 99% and it goes under the 400 kb limit.)

Quote from Victor :

I don't think LFS can make use of png files at the moment,

For previewing I always "trick" the Skinviewer by renaming the exported .png files (from Inkscape) to XFG_mySkin.png.jpp
Works for LFS.exe too.

It is just bit strange that I have to convert files to make them bigger.
Quality wise there is not much difference, not sure how much traffic or storage matter.
I noticed several times that my skins as png were smaller than the jpg versions.y


jpg and png compress different, so it depends on image content what is better.
This livery might work better as png:

-clear lines
-large areas with one shade of color

This livery might work better as jpg:

-no large areas of same color
-color gradients

Quote from TFalke55 :

The only place where I could immagine a practical advantage of png skins was, if the windows were skinable *cough* for example for something like this *cough*

That might be cool too. Skin templates have some empty areas that could be used.
But not sure how compability with jpg would work and many current skins paint into the "empty" areas. Main use would be flag/number/name which could be in driver profile, like license plate. But goes bit offtopic now..

Thanks for the explanation, but I did know how png works and differs from jpg
Though I did not know that LFS (or I guess directx) will load png just fine if you give it the jpg extension.

We'll see about all this when Scawen makes some time to do the skin download updates.
I like the idea of converting skins to dds on the server and gzipping them. The filesize is about the same as jpg then (even for 2048) but without lossy compression. It also has the added bonus that the LFS client doesn't have to do any conversions, leading to faster skin downloading / processing.

I knew that you would know, just thought maybe interessting for others.
("png skins would be better in every case")
Anyway, guess the other thread about skins covers everything now.