The popularity and availability of Android devices have motivated researchers to implement their image processing systems on Android mobile platform. Retinex is considered as an effective method to restore the image's original appearance and used as a pre-processing step in many computer vision applications. It would give a lot of benefits to implement Retinex on such portable system and optimize it for real-time performance. This is a challenge because of limited computational power and memory of the portable system. This paper presents an implementation of rsRetinex, an optimized Retinex algorithm by using Renderscript technique. The experimental results show that rsRetinex could gain up to five times speedup when applied to different image resolution. © 2014 Springer Science+Business Media Singapore.