双二次B-样条插值图像缩放

双线性和各种双三次插值方法是图像缩放中常用方法，但是双二次插值函数却很少被人提起。本文提出了一种基于双二次B-样条局部插值的图像缩放方法，该算法在图像局部重构过程中对称地采用了4×4采样点，并通过对该函数进行重采样来实现图像的缩放，避免了二次函数在图像重构与采样中的相位失真问题，此算法是一个局部性算法，易于扩展。实验结果表明，本文算法得到的图像的峰值信噪比(PSNR)、MISSIM值比双线性插值、双三次卷积、Catmull-Rom三次插值、Dodgson插值算法都要好，接近于最好的双三次B-样条算法，视觉效果虽然不如双三次B-样条插值算法，但优于Dodgson方法，计算时间比双三次B-样条减少了近三分之一。由于该算法没有对图像边缘特征进行特殊处理，对于一些细节纹理比较丰富的图像，将进一步研究。

Image resizing via bi-quadratic B-spline interpolation

Bilinear interpolation and various bi-cubic interpolations are frequently adopted in image resizing. However the bi-quadratic function is rarely considered due to its phase distortion problem. In this paper, we propose an image resizing method via bi-quadratic B-spline interpolation, where 4×4 pixels are sampled symmetrically in the local image. and resamping the image with the function,Thus the phase distortion problem can be avoided. The proposed algorithm is a local algorithm and can be easily extended.According to our experiment results,the proposed bi-quadratic B-spline interpolation algorithm has better image peak signal-to-noise ratio (PSNR) and MISSIM than bi-linear interpolation, bi-cubic convolution, Catmull-Rom cubic interpolation, or the Dodgson interpolation algorithm.The results are comparable to the bi-cubic B-spline interpolation algorithm,though the visual effects are not as good as that,but still better than the Dodgson algorithm. The computing time is reduced by nearly one-third compared to the bi-cubic B-spline interpolation algorithm.Since the algorithm has not carried on the special handling to the image edge features,so the method does not suit the rich details texture images,which we will focus on in the future days.