Extracting watermarks from printouts captured with wide angles using computational photography
|Author:||Pramila, Anu1; Keskinarkaus, Anja1; Takala, Valtteri1;|
1Center for Machine Vision and Signal Analysis, University of Oulu, Oulu, Finland
|Online Access:||PDF Full Text (PDF, 7.4 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2019090426731
|Publish Date:|| 2019-09-04
Thus far the research of print-cam robust watermarking methods has focused on finding new methods for embedding and extracting the watermark. However, the capturing process itself, has been neglected in scientific research. In this paper, we propose a solution for the situation when the watermarked image has been captured in a wide angle and the depth of focus of the camera is not deep enough to capture the whole scene in-focus resulting in unfocused areas. The solution proposed here relies on a subfield of computational photography, namely all-in-focus imaging. All-in-focus images are generated by fusing multiple images from the same scene with different focus distances together, so that the object being photographed is fully in focus. Traditionally, the images to be fused are selected by hand from the focal stack or the whole stack is used for building the all-in-focus image. In mobile phone applications, computational resources are limited and using the full focal stack would result in long processing times and the manual selection of images would not be practical. In addition, we propose a method for optimizing the size of the focal stack and automatically selecting appropriate images for fusion. It is shown here that a watermark can still be recovered from the reconstructed all-in-focus image accurately.
Multimedia tools and applications
|Pages:||16063 - 16084|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
113 Computer and information sciences
213 Electronic, automation and communications engineering, electronics
This work was supported in part by Finnish Cultural Foundation.
© Springer Science+Business Media New York 2016. This is a post-peer-review, pre-copyedit version of an article published in Multimed Tools Appl. The final authenticated version is available online at: https://doi.org/10.1007/s11042-016-3895-z.