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.