How can I make to create a perfect sprite with trasparency around it?
I don't want this!
(http://img20.imageshack.us/img20/6794/immaginein5.th.jpg) (http://img20.imageshack.us/my.php?image=immaginein5.jpg)
Help!
what color background is he painted on?
You will always see any sprite displayed on "magic pink" in the AGS editor. In the game it will look okay because everything pink isn't displayed.
It doesn't really matter what background colour you use in your paint program; when importing you can simply check "use top-left pixel" (or whatever) as transparent colour.
A good tip is to use a colour as background that can be easily distinguished from any colour used in the sprite, and then take care that one of the corner pixels has that colour.
To get rid of the white lines shouldn't be too tricky, too. I think you've merged a non-solid black line with the magic pink here. A simple yet effective method is, in Photoshop, to "fill outline", select a pixel width of 1, set it to "middle", then have all the blurry stuff removed.
Like I said in your other thread (http://www.adventuregamestudio.co.uk/yabb/index.php?topic=29500.0), this is really about how you make and save the images in Photoshop, and so isn't an AGS question. Try a forum search for 'anti aliasing', since that's what's causing the problem, and there've been many suggestions for ways to resolve it in Photoshop.
If you save your PNGs with a transparent background (not white, as it looks like you are doing), then the alpha transparency shouldn't be a problem. (I think - I'm not particularly good at art OR Photoshop, but that's worked in the past.)