JPEG Compression Protection
Many photo hosting and web proxies compress JPEG files to speed up downloads. In this regard, Cambridge specialists came up with the idea of adapting the well-known Tovalds algorithm for protecting notes from copying to JPEG images. They developed a grid that generates moire upon re-compression ( demo using a Google WAP proxy).
If you are behind a recompressed firewall, then VOID will appear on both images.
For more information about the algorithm, see Towards copy-evident JPEG images , which is published in Lecture Notes in Informatics.
Such grids for generating moire are often used to protect various financial documents, including banknotes, tickets and checks. The idea is that when scanning or copying artifacts or obvious distortion of the grid appear.
Original image
Photocopy
In this paper, the algorithm is adapted specifically to the JPEG algorithm so that the distortions introduced by the algorithm manifest themselves as much as possible and display an inscription that is not visible on the original image.
Researchers are now working to adapt the system for video streams in which compression algorithms behave less predictably. Then it can be used to protect the original content from illegal copying.
| Original image | After recompression |
 |  |
For more information about the algorithm, see Towards copy-evident JPEG images , which is published in Lecture Notes in Informatics.
Such grids for generating moire are often used to protect various financial documents, including banknotes, tickets and checks. The idea is that when scanning or copying artifacts or obvious distortion of the grid appear.
Original image
Photocopy
In this paper, the algorithm is adapted specifically to the JPEG algorithm so that the distortions introduced by the algorithm manifest themselves as much as possible and display an inscription that is not visible on the original image.
Researchers are now working to adapt the system for video streams in which compression algorithms behave less predictably. Then it can be used to protect the original content from illegal copying.