Example at: http://lennym.github.com/Instagram-Deshredder-Challenge/

Only tested on the sample image provided by Instagram as part of the Challenge at 
http://instagram-engineering.tumblr.com/post/12651721845/instagram-engineering-challenge-the-unshredder.

Image needs to be kept locally in order to satisfy the same-origin restrictions in Canvas getImageData.

Columns of pixels are compared fairly crudely by counting the number of adjacent pixels which differ by 
more than a given Euclidean distance (technically the square of the Euclidean distance). This given value
is provided as a parameter when constructing the deshredder and defaults to 100 (which worked well enough
for the test image). It might need some tinkering for other images. Who knows?