An investigation into aliasing in images recaptured from an LCD monitor using a digital camera

Abstract

With current technology, high quality recaptured images can be created from soft displays, such as an LCD monitor, using a digital still camera and professional image editing software. The task of verifying the ownership and past history of an image is, consequently, more difficult. One approach to detecting an image that has been recaptured from an LCD monitor is to search for the presence of aliasing due to the sampling of the monitor pixel grid. To validate this approach, an investigation into the aliasing introduced in a digitally recaptured image is conducted. An anti-forensic method for recapturing images that are free from aliasing is developed using a model of the image acquisition process. This is supported by a simulation of the acquisition process and illustrated with examples of recaptured images that are free from aliasing.