Perceptual modeling of media signals based on local contrast and directional edges

摘要

A perceptual model performs an analysis of a media signal, such as an image or audio signal. The model may be used in media signal processing applications such as digital watermarking and data compression to reduce perceptibility of changes made to code the signal. For image applications, the model computes the sensitivity of an image to changes based upon local image contrast, while taking into account the sensitivity of connected directional edges. By comparing the local image strength of various directionally filtered versions of the image, the model creates a directional control vector. This control vector may be used to reduce changes to an image in text and edge regions, and thus, avoid perceptible artifacts in those regions. The model takes into account the local contrast of the image and the directional control vector to create a gain vector. Using the local contrast measurements, the model follows the eye's nonlinear response to contrast discrimination.