Intra picture coding with planar representations

In this paper we introduce a novel concept for Intra coding of pictures especially suitable for representing smooth image segments. Traditional block based transform coding methods cause visually annoying blocking artifacts for image segments with gradually changing smooth content. The proposed solution overcomes this drawback by defining a fully continuous surface of sample values approximating the original image. The gradient of the surface is indicated by transmitting values for selected control points within the image segment and the surface itself is obtained by interpolating sample values in-between the control points. This approach is found to provide up to 30 percent bitrate reductions in the case of natural imagery and it has also been adopted to the initial HEVC codec design by JCT-VC.