利用低通滤波器对图像进行插值放大：按放大的倍数对原图像进行插零，插零后的图片与低通滤波函数进行卷积，原先插入的零的位置自动替换为适当的插值，如此图像就已经插值放大了，图像质量还不错。-Double the number of pixels of each row and column by adding a zero value pixel between each pixel of the image.Then operate with two kinds of low-pass filter