ArtBistro

Unfortunately if those are the only formats they accept then you are going to encounter some lossy to your artwork. The good thing is that we won't notice. Your artwork will still look like it does on your computer just in a much smaller file size, plus no one will be able to rip off your work because of the lower quality. Thats one of the reasons they have those limitations. Art Bistro tries really hard to protect the work of the artists who post their work here. So by not accepting source file documents the help ensure someone can't use your work easily. The other reason is to garauntee that everyone can read and view the files. With all the extensions you named here it would be a nightmare trying to work out compatability with the entire internet and your personal versions of the softwares you used. So these formats simplify things because they are the web standards for photos. It also helps with page load speed and all the other issues with memory and the internet. Their servers are only so big.

ok, with all that said if you want to convert all your files into these formats all you have to do is export the file as the chosen format. I think in illustrator you can do it through the save as function as well. its a pretty simple process, it just gets time conssuming the more documents you have to convert.

Hope this helped,

Josh

If you have Photoshop, you don't have to go through any process as phoenix points out; just go to File>Save for Web.

You will be given a number of choices for format: GIF, JPG & PNG, each with two or three quanlity setting for each. Setting color space and quality will change the size of the image in terms of kilobytes.

GIF is the best format for images with large, unmodulating color fields; JPEG is best for Photos. If you make an overall Photoshop file and then import all your images into it, you can then do a batch process to save them for output.

Gifs files are great for grayscale or works with solid colors and no shading, pixel created with palettes, but not much else.  They do support transparent backgrounds and frame animation.

JPGs suck.  Period.  Even the highest quality contains annoying artifacts.

PNGs are the most ideal format as it supports full color, compresses without artifacts(unlike jpgs), supports transparent and translucent color information.

Of course in black and white or art with a computer palette(256 colors) takes up less space with gif files.  I had some kind of presentation chart I sent to the folks who are working on Mo Mini's Studio, a cellphone game creation suite(still in development), about the benefits of using gif files.  Apparently there program converts gifs into pngs once imported.  It creates a noticable difference when you're dealing with 100's of sprites and tiles.  Don't have it on hand at the moment though.