Single-Scale Retinex Using Digital Signal Processors
Glenn D. Hines, Zia-ur Rahman, Daniel J. Jobson, Glenn A. Woodell · 2005
nasa.gov as.wm.edu nasa.gov nasa.gov The Retinex is an image enhancement algorithm that improves the brightness, contrast and sharpness of an image. It performs a non-linear spatial/spectral transform that provides simultaneous dynamic range compression and color constancy. It has been used for a wide variety of applications ranging from avi-ation safety to general purpose photography. Many potential applications require the use of Retinex pro-cessing at video frame rates. This is difficult to achieve with general purpose processors because the algorithm contains a large number of complex com-putations and data transfers. In addition, many of these applications also constrain the potential archi-tectures to embedded processors to save power, weight and cost. Thus we have focused on digital signal pro-cessors (DSPs) and field programmable gate arrays (FPGAs) as potential solutions for real-time Retinex processing. In previous efforts we attained a 21 (full) frame per second (fps) processing rate for the single-scale monochromatic Retinex with a TMS320C6711 DSP operating at 150 MHz. This was achieved af-ter several significant code improvements and opti-mizations. Since then we have migrated our design to the slightly more powerful TMS320C6713 DSP and the fixed point TMS320DM642 DSP. In this paper we briefly discuss the Retinex algorithm, the performance of the algorithm executing on the TMS320C6713 and the TMS320DM642, and compare the results with the