Perceptual Criteria on Image Compression

Perceptual Criteria on Image Compression

Place: Sala d'Actes del CVC

Affiliation: Centre de Visió per Computador  

Nowadays, digital images are used in many areas in everyday life, but they tend to be big. This increment of the amount of information leads us to the problem of image data storage. For example, an image at a resolution of 512x512 that allocates 24 bits per pixel, occupies 786,432 bytes. That is why image compression is important.

An important feature of image compression is that it can be lossy or lossless. A compressed image is acceptable provided these losses of image information are not perceived by the eye. It is possible to assume that a portion of this information is redundant.

In lossy compression, current image compression schemes remove information considered irrelevant by using mathematical criteria. One of the problems of these schemes is that although the numerical quality of the compressed image is low, it shows a high visual image quality, e.g. it does not show a lot of visible artifacts. It is because these mathematical criteria, used to remove information, do not take into account if the viewed information is perceived by the Human Visual System. Therefore, the aim of an image compression scheme designed to obtain images that do not show artifacts although their numerical quality can be low, is to eliminate the information that is not visible by the Human Visual System.

Hence, this Ph.D. thesis proposes to exploit the visual redundancy existing in an image by reducing those features that can be unperceivable for the Human Visual System.