Perceptual image quality improvement for large screen displays

摘要

To display a low-resolution digital image on a large screen display with a native resolution that reaches or exceeds the well-known HDTV standard, it is desirable to re-scale the image to full screen resolution. However, many well known re-scale algorithms, such as cubic spline interpolation or bi-cubic interpolation filters, only reach limited performance in terms of perceived sharpness and leave contour artifacts like jaggedness or haloing, which easily appear above the threshold of visual perception with regard to a reduced viewing distance. Since human vision demonstrates a non-linear behavior towards the detection of these artifacts, we elaborate some simple image operations that better adapt to the image quality constraints imposed by most of the linear methods known to us today. In particular, we propose a nonlinear method that can reduce or hide the above-mentioned contour artifacts in the spatial frequency domain of the display raster and increase perceived sharpness to a very noticeable degree. As a result, low-resolution images look better on large screen displays due to an enhanced local contrast and show less annoying artifacts than some of the classical approaches reviewed in this paper.