基于NSCT的区域自适应图像插值算法

摘要

Image interpolation plays a vital role in digital image processing.In order to preserve image texture detail and edge sharpness,a new method of region adaptive image interpolation based on NSCT (nonsubsampled contourlet transform) is proposed.Image is divided into different regions and interpolated by different methods respectively.Firstly,a new type of C2 continuous rational function interpolation model is constructed,and the error estimates are given.Secondly,image edge contour information is captured by the NSCT,and the image is divided into edge region and non-edge region adaptively according to a preset threshold.Finally,as for edge region,edge-directed interpolation technique is used to get high resolution image.Similarly,rational function interpolation algorithm is used in non-edge region.The objective image with higher resolution ratio than the input image is obtained by adaptive interpolation.Compared with the classical image interpolation algorithm,the proposed method is highly competitive not only in PSNR (peak signal to noise ratio) and SSIM (structural similarity index) but also in visual effect.Experimental results show that the proposed algorithm not only has lower time complexity,but also can preserve image details,eliminate phenomenon of edge aliasing,and have a high quality of interpolation image.%提出一种基于非下采样轮廓波变换(nonsubsampled contourlet transform,NSCT)的分区域自适应插值算法,将图像划分为不同区域,相应地采用不同的方法实现图像插值.首先,构造了一类有理函数插值模型,分析了其C2连续性条件,给出了误差估计.其次,通过NSCT捕获到图像的边缘轮廓信息,利用其高频信息的统计特性设定阈值,根据阈值将图像自适应地划分为边缘区域和非边缘区域.最后,边缘区域采用新的基于边缘指导的插值(new edge-directed interpolation,NEDI)模型,非边缘区域采用C2连续有理函数模型插值,进而得到目标图像.实验结果证明:提出的基于NSCT的区域自适应插值算法与当前经典插值算法相比,在处理图像纹理细节和边缘方面具有明显优势,同时获得了较好的客观评价数据,且时间复杂度较低.