Lossless embedding of depth hints in JPEG compressed color images

•A compressed-domain lossless data hiding scheme is adopted to embed depth hints.•Joint color and depth image processing is used to extract depth hints.•The best possible depth hints are found under the watermark capacity constraint.•The proposed method enables the end-user to reconstruct depth images.•A promising image refocusing application is shown.

The conventional JPEG compressed domain lossless data hiding scheme has three attractive properties: file size is maintained, decoded image is unchanged, and embedded bitstream is compatible with the JPEG standard. This study introduces a new application of the compressed domain lossless data hiding scheme. Specifically, we present an algorithm that embeds depth hints to a compressed bitstream of a color image, which enables the end-user to extract depth hints and reconstruct the depth image. On the limited watermark capacity, depth hints are obtained using super-pixel color image segmentation and depth value clustering. The experimental results demonstrate the effectiveness of the proposed algorithm.