Franz Enzenhofer built this cool feature that lets you draw a picture (or take a picture of yourself with your webcam) and then search Google Images using the search by image feature based on your drawing.

I decided to draw elmo, which can often turn bad because I am not a good artist. But here is a video demo of it in action:

To play with this tool yourself, go to Franz’s web site.

He explained how it works:

You draw something on an HTML5 canvas.
Click on Search
Image gets converted into a base64 encoded data uri
Image data gets send to server (powered by Heroku)
Image gets uploaded to Amazon S3
The Amazon S3 Image URL gets communicated back to your browser.
Browser gets redirected to Google Search by Image

Pretty smart!

Forum discussion at Google Blogoscoped Forums.