摘要：Images play a vital role in steganography, as cover media to hide secret messages. Retargeting becomes mandatory while transmitting image in a heterogeneous network because sender and recipient may not have display devices of same resolution. Resizing images by scaling or cropping also lead to loss of visually important features. In steganography, resizing, compressing, and changing the color or format of stego images would result in loss of hidden information. In this paper we attempt to retarget stego images in a content preserving manner using a modified seam carving technique called PSC. Content in this context refers to the visually salient features in the cover image as well as the secret message hidden within it. The cover image is first subjected to PSC to extract as many seams leaving the segments containing ROIs intact. Based on the size of secret message segment(s) containing the ROIs are selected to encode the secret message and is transmitted to the receiver. The seams are also encoded separately in the reverse order of their extraction, so that on the receiver end the receiver would download all the image segments containing the ROIs and as many seams as required to constitute an image that fits into the target device. The retargeted image contains the secret message intact which could be decoded by the receiver.
关键词：PSC-Piecewise Seam Carving; ROI-Region of Interest; Retargeting; Steganography
