Do you want to save the file to your hard drive or website?
If the hard drive may have a hard time if you are not using Air. Due to the secure Flash sandbox, you cannot write arbitrary files to the user's hard drive.
If you absolutely must save it to the user's hard drive using Flash rather than Air, you will probably have to send the bitmap data to a server-side PHP (or similar) script, which will then allow the user to load and save the image in one place or another .
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