Algorithm And Hardware Implementation Of Low-Complexity Cubic Convolution Spline Interpolation

Image interpolation algorithm is a basic and important branch of image processing and plays an irreplaceable role.Images of military radar,medical image processing,image compression,and image resolution adjustment all need image interpolation technology.Traditional image interpolation algorithms include the nearest neighbor interpolation algorithm,bilinear interpolation algorithm and cubic convolution interpolation(CCI)algorithm.Because of the inherent limitations of these interpolation algorithms,the reconstructed images obtained after interpolation easily have jagged edges or blurring details.A cubic convolution spline interpolation(CCSI)algorithm based on least-square method is proposed to solve the shortage of traditional interpolation algorithm.Simulation shows that CCSI algorithm is superior in performance and can be cooperate with discrete cosine transform(DCT)-based image or video codec to improve the performance for a variety of high compression ratio.However,CCSI algorithm has the disadvantages of high computational complexity and cumbersome steps,so that the application of the algorithm is limited and the research on hardware implementation is missing.In order to reduce the computational complexity of CCSI algorithm and investigate its FPGA implementation,this paper does the following research work:1.Systematic review and performance analysis of the image interpolation technologies,including traditional linear interpolation algorithm and CCSI algorithm.2.For the CCSI algorithm,the 11 filter coefficients of direct computation algorithm used to calculate the circular convolution are reduced to 5 by extending the boundary conditions of the CCI function.Thus,a low-complexity direct computation algorithm for CCSI scheme is proposed.The simulation results indicate that the proposed algorithm can reduce the computational complexity while still maintaining the subjective and objective quality of the reconstructed image.3.The traditional two-step CCSI algorithm is simplified.Moreover,the boundary conditions are extended to reduce the number of required filtering coefficients.Thus,a new simple direct computation of CCSI is proposed.The simulation results show that the proposed algorithm can simplify the computational step with almost the same subjective and objective performance,thereby being easily implemented by a pipeline structure.4.The hardware implementation of CCSI algorithm is investigated.The CCSI decimation module and CCI interpolation module are implemented on FPGA.