线性低通滤波器最常用的是线性平滑滤波器，这种滤波器的所有系数都是正的，也称邻域平均。邻域平均减弱或消除了傅立叶变换的高频分量，对噪声的消除有所增强，但是由于平均而使图像变得更为模糊，细节的锐化程度逐渐减弱。
下面使用不同的平滑模板对图像进行滤波：（二维线性滤波fliter2）(The most commonly used linear low-pass filter is the linear smoothing filter, which has all the positive coefficients, also known as the neighborhood average. Neighborhood average eliminate or decrease the frequency component of Fourier transform, the elimination of noise increased, but the average and make the image more fuzzy, details sharpening level gradually.
The image is filtered by using different smooth templates (2d linear filtering fliter2))