利用小波进行硬阈值和软阈值去噪，将二者进行比较，并采用峰值信噪比评价图像质量，画出硬阈值和软阈值两种方法的峰值信噪比随噪声方差的变化曲线。-Using wavelet hard threshold and soft thresholding, we will compare the two and uate the image quality using a peak signal to noise ratio, change PSNR draw hard threshold and soft