HDR image encoding using reconstruction functions based on piecewise linear approximations

Abstract

Two-layer encoding schemes for HDR images can not only reduce the storage requirements, but more importantly they can also ensure backward compatibility as imaging technology makes the transition from LDR to HDR. In this paper, we present a two-layer lossy encoding scheme for HDR images, which models each channel of the HDR image as a piecewise linear function of its tone-mapped version, to reduce the dynamic range of the residual image and achieve a better compression. The tone-mapped image and the residual image for each channel are saved as two separate LDR images, and these along with the piecewise linear models, encode the details of the HDR image. The encoded images are compatible to both HDR and non-HDR enabled devices for visualization and processing. Detailed comparison with similar existing state of the art two-layer techniques is presented to show the effectiveness of our proposed scheme.