1.实现对lena.bmp灰度图像的快速傅立叶变换,并求其变换后的系数（幅度）分布； 2.实现对lena.bmp图像做离散余弦变换,选择适当的DCT系数阈值对其进行DCT反变换 ；-1 to achieve the fast Fourier transform on lena.bmp grayscale image, and to find the transformed coefficients (amplitude) distribution 2. To achieve lena.bm