Here is how I turned a photo into a pattern:
Pick a photo of your choice.
School photos work very well as the lighting is good and the face is usually without shadows
Use any photo editing software of your choice. There are lots of free software available online. I use Picnik. Use the posterize function to get this effect. Play around with the colours until you are happy. I settled on 10 colours.
Save the posterized picture and go to the Pencil Sketch function. Without any further editing I got this result. Play around until you are happy with the amount of lines and the clarity of the picture.
You can use the picture as is, or further simplify it by hand. I printed the previous picture and traced it against the window (you can use a light table if you are more sophisticated than me!). Here you can make it as simple or as complicated as you wish.
I scanned this version into my computer and printed it on to a wash-away stabilizer.
And Voila! A perfect embroidery pattern.
A friendly request:
This is a picture of my son. I used it to demonstrate the process.
Please feel free to link to this tutorial, but please do not re-post this whole post with pictures to your blog. If you need one picture to illustrate the post, use one of the sketches.