Multimedia Security, Volume 1

4Invisibility

Pascal LEFÈVRE¹, Philippe CARRɹ and David ALLEYSSON²

¹ XLIM, CNRS, University of Poitiers, France

² LPNC, Grenoble Alpes University, Savoie Mont Blanc University, CNRS, Grenoble, France

In this chapter, we intend to discuss the different strategies to ensure the invisibility of a message embedded in a color image. The term “invisibility” here relates to the visual aspect. For grayscale images, many solutions have been developed, attempting to take into account the modeling of the human visual system (HVS) in order to limit degradation. However, the extension of these solutions to color images often proposes an adaptation of the strategies dedicated to grayscale images, configured by a wise choice of a color component. Even when a dedicated approach to color is introduced (such as through the use of quaternion formalism), the same challenge is present; in other words, the correct choice of the direction of the insertion color. In this chapter, we discuss these aspects and we conclude by introducing a method configuring this choice of color direction, depending on psycho-visual considerations.

4.1. Introduction

In this chapter, we focus on the watermarking of color images that involves the current framework of modern watermarking algorithms. In this book, different watermarking methods for color images are presented, however, many of them proceed in a similar way: selecting a chromatic or achromatic channel in order to have only one scalar detail to manipulate ...