(Please, read it totally and carefully before trying to change anything, or read only the bold lines at the end of the post)
And most of us have add an error saying that we don't have the right to import a spray. Well, it seems it's another Valve bug.
To fix this error, the solution is to change the steam language to English (I found this solution on the web), then import the spray, and then, if you want, reset your language to the one you prefer. This solution involve that you close Steam after each language changes. And, if the error doesn't appear anymore, the imported file don't seem to be imported at all. So, I started to do some try, in order to see what happens when importing a picture. And after 30 minuts of test, all became clear.
Why this new error? Again because there is a lack of rigor in the Valve development team. The Steam interface lets you choose the file where you want, but if the file isn't in the right directory, this don't work. The imported file must be placed in the "%yourDrive%\Valve\Steam\SteamApps\%YourSteamAccount%\half-life 2 deathmatch\hl2mp\materials\VGUI\logos".
In fact, the importer create the vmt file in that directory, but if your picture wasn't in that directory, the vmf file isn't created in that directory, and the spray can't be nor displayed, nor choosed.
Now you can import the pictures that you included in that directory (if their extensions matches with those given by Valve (gif don't work, if you want transparency, you use TGA with an alpha layer)). (I only tried with square picture having a size of a power of 2).
Well, it was not so hard.
You can reset your language, but if you want to import a new spray?
It seem's that it works, now you have also the right to import in your langauge.
Why? Because the directories needed (VGUI in hl2mp and logos in VGUI) are now created. So its another way to do it: just create those directories, and then copy the files you want in it. But, for two reason, this way isnt a good one. First, while doing that, you don't create the vmt associated to the standard spray, so that those aren't usable. You can choose one of them, but they aren't displayed on the wall. Th other reason is tha another directory, in the logo file (called UI), and its files arent created. Those files permit you to see a thumbnail of the tags in the option panel.
So, I resume the good way of doing it:
- 1) Change the Steam Language to English.
2) Restart Steam
3) Launch HL2DM (so that the needed directories and files are created).
4) Copy the file you want in "%yourDrive%\Valve\Steam\SteamApps\%YourSteamAccount%\half-life 2 deathmatch\hl2mp\materials\VGUI\logos" and import your new spray.
5) Enjoy the game, and if you want change your language back.