Steps towards ´undigital´ intelligent image processing: real-valued image coding of photoquantimetric pictures into the JLM file format for the compression of portable lightspace maps

Recent advances in intelligent signal processing have made it possible to capture high dynamic range images which are better represented as an array of real numbers rather than the current convention of an array of integers. This paper proposes a solution to address the need for real, rather than just integer, image coding and file formats. Additionally, we propose that the real-valued data be linear in photoquantity (the quantity of light received by the camera) to avoid the image misrepresentation that occurs when a camera´s non-linear dynamic range compressor and a display´s dynamic range non-linear expander do not match. We present two novel image formats that achieve this: the portable lightspace map (PLM) and its compressed version the JPEG lightspace map (JLM), that builds upon the JPEG compression scheme. The results of various compression levels for real-valued data and their corresponding file sizes are reported.