Implementing image processing applications in embedded systems is a difficult challenge due to the drastic constraints in terms of cost, energy consumption and real time execution. Reconfigurable archi-tectures are good candidates to take-up this challenge and especially when the architecture is able to support different word-lengths of pixel through Sub-Word Parallelism (SWP) capabilities. Exploiting the diversity of supported data-types requires automation tools able to optimize the data word-length under an accuracy constraint. In this paper, a new approach for word-length optimization in the case of SWP operations is proposed. Compared to existing approaches the optimization time is significantly reduced without sacrificing the quality ...