Here's a research report on "unblurring" information on checks and credit-cards that has been scrambled with the Photoshop "mosaic" effect — this guy claims that he can extract the hidden numbers.
What does this mean? Well, let's take the mozaic version of 0000001 (zoomed in):
… and identify the brightness level (0-255) of each mozaic region, indexing them in some consistent fashion as a=[a_1,a_2…,a_n]:
In this case, the account number 0000001 creates mozaic brightness vector a(0000001)=[213,201,190,…]. We find the mozaic brightness vector for every account number in a similar fashing using a script to blur each image and read off the brightnesses. Let a(x) be the function of the account number x. a(x)_i denotes the ith vector value of the mozaic brightness vector a obtained from account number x. Above, a(0000001)_1 = 213.
We now do the same for the original check image we found online or wherever, obtaining a vector we hereby call z=[z_1,z_2,…z_n]
(via /.)
