Two-step evolution of polymorphic circuits for image multi-filtering

This paper proposes to implement multifunctional image filters using multifunctional gates such as polymorphic gates or multiplexed ordinary gates. The design procedure is based on evolutionary design and optimization conducted using Cartesian genetic programming (CGP). Because of the complexity of the problem the design is decomposed to two phases. In the first step, a multifunctional filter is evolved at the register-transfer level (RTL) using a set of processing elements containing functions such as minimum/maximum, minimum/average etc. over two pixels. In the second step, gate-level implementations of the processing elements utilized in evolved filters are designed and optimized using CGP in combination with conventional logic synthesis tools. It is shown that resulting filters exhibit good filtering capabilities. They are also area-efficient in comparison with solutions based on multiplexing of ordinary filters.