How can I store raw data in an image file?

I have some raw data in a file that I would like to store in an image file (bmp, jpg, png, or even gif (eegad)). I would like this to be a two way process: I need to be able to reliably convert the image file back later and get a file that is identical to the original file.

I am not looking for a how-to on steganography; the image file will probably be one pixel wide and millions of pixels high and look like garbage. That is fine.

I looked into the Imagemagick utility convert, but am intimidated by the large number of options and terse man page. I am guessing I could just use this to convert from a 开发者_如何学C'raw' black channel to png, but would have to specify a bunch of other stuff. Any hints? I would prefer to work within Imagemagick or using Linux utilities.

If you are wondering, there's nothing black hat or cloak and dagger about my request. I simply want to automatically backup some important data to a photo-sharing site.

I'd plow into ImageMagick if that's what you'd prefer anyway.

Specific image formats support storing text data to different degrees, and ImageMagick supports all of the formats you mentioned. I'd choose the one that lets you store what you need.