High quality image reconstruction from RAW and JPEG image pair

Abstract

A camera RAW file contains minimally processed data from the image sensor. The contents of the RAW file include more information, and potentially higher quality, than the commonly used JPEG file. But the RAW file is typically several times larger than the JPEG file (taking fewer images, slower quick shooting) and lacks the standard file format (not ready-to-use, prolonging the image workflow). These drawbacks limit its applications. In this paper, we suggest a new “hybrid” image capture mode: a high-res JPEG file and a low-res RAW file as alternative of the original RAW file. Most RAW users can be benefited from such a combination. To address this problem, we provide an effective approach to reconstruct a high quality image by combining the advantages of two kinds of files. We formulate this reconstruction process as a global optimization problem by enforcing two constraints: reconstruction constraint and detail consistency constraint. The final recovered image is smaller than the full-res RAW file, enables faster quick shooting, and has both richer information (e.g., color space, dynamic range, lossless 14 bits data) and higher resolution. In practice, the functionality of capturing such a “hybrid” image pair in one-shot has been supported in some existing digital cameras.