Abstract

Most camera images are saved as 8-bit standard RGB(sRGB) compressed JPEGs. Even when JPEG compres-sion is set to its highest quality, the encoded sRGB imagehas been significantly processed in terms of color and tonemanipulation. This makes sRGB-JPEG images undesirable for many computer vision tasks that assume a direct rela-tionship between pixel values and incoming light. For such applications, the RAW image format is preferred, as RAW represents a minimally processed, sensor-specific RGB im-age with higher dynamic range that is linear with respect to scene radiance. The drawback with RAW images, how-ever, is that they require large amounts of storage and are not well-supported by many imaging applications. To address this issue, we present a method to encode the necessary metadata within an sRGB image to reconstruct a high-quality RAW image. Our approach requires no calibration of the camera and can reconstruct the original RAW to within 0.3% error with only a 64 KB overhead for the ad-ditional data. More importantly, our output is a fully self-contained 100% complainant sRGB-JPEG file that can be used as-is, not affecting any existing image workflow the RAW image can be extracted when needed, or ignored otherwise. We detail our approach and show its effectiveness against competing strategies.