Linear Minimum Mean Square Error Demosaicking
Résumé
Today, digital cameras are ubiquitous. One can be purchased for the price equivalent to a night's stay in a hotel in occidental countries, or we receive it for “free” when acquiring a mobile phone or a laptop computer. The existence of such a common and ultimately cheap device is due to the fundamental developments in the way an image is acquired by the sensor and processed by the microcomputer embedded in the camera. These developments would not have been possible without recent breakthroughs in digital color image processing. In this chapter, we focus on the sampling of images by a single camera sensor and on the subsequent digital image processing necessary to mimic the fact that a color image has three different color responses at each spatial position [2]. These image processing steps are called demosaicing (or demosaicking) algorithms. We highlight the properties of the human visual system (HVS) that have been exploited in the development of digital cameras in general and demosaicking in particular. The working of the human visual system is still a source of inspiration today because it has capabilities that are not yet taken into account in digital cameras. In particular, we discuss how the random nature of the arrangement of chromatic samples in the retina can improve the color sampling by digital cameras.