中文说明：加权中值滤波，用于图像增强，只用于超声图像，对超声图像去噪有很好的效果。内还包括信噪比计算方法。
English Description：
Weighted median filter, used for image enhancement, only used for ultrasonic image, has a good effect on ultrasonic image denoising. The signal-to-noise ratio calculation method is also included.