Instant Sprite was created to deal with some issues I had when generating CSS Sprites. There are some tools online which work great, but require extra steps before generating the sprite (such as zipping up all the images). Instant Sprite allows you to make tweaks to the settings and instantly see the results.
Hopefully you find it useful too - it is a work in progress, so leave me some feedback if you find any bugs, typos, or just want to leave a comment.
I have written a number of articles to hopefully help you hit the ground running with CSS sprites.
If you are just starting out, I would recommend What Are CSS Sprites to get a grip on the basics of sprites.
No. Instant Sprite does not upload anything to a server, everything is kept on your computer. It does this by using the Canvas and File API provided in upcoming versions of HTML and JavaScript to run only inside your browser.
Instant Sprite uses some features that are not fully supported by all browsers, most notably the File API.
At the time of writing, the browsers that support this are:
Yes. See the code at http://github.com/bgrins/InstantSprite. Additionally, Instant Sprite makes use of some excellent open source software. Here is a listing:
The original work was done by Brian Grinstead. Any other contributors will be listed on the contributors page for the project.