There is a web application here called KnitPro
which allows you to upload photos and convert them into a knitting pattern. I haven't tried it myself, so I don't know what the end result will be like.
You will have to scan the picture and possibly manipulate it in something like Photoshop or Paintshop Pro, as it needs to be under 1 MB in size and in Jpg, gif or png format. If you can't do this yourself, you should be able to get it done at somewhere like a photography or reproduction shop.
By the way, software is also available at PC World and the like which allows you to do a similar job. I've only seen the ones which are used for converting photos to cross stitch/needlepoint charts though. If you try to use these to generate a knitting pattern, you'll find that when the picture is knit, it will look strangely elongated! This is due to the knit stitch being more rectangular than a cross stitch. Make sure that the application you choose is specifcally for knitting patterns.