实现了多种空域、频域滤波器：直方图均衡化、中值滤波、拉普拉斯锐化、理想低通、巴特沃斯低通、去条带-realize various space-based and frequency-based filters, like equilzation, median filter, laplacian filter, ideal low-pass filter, Butterworth low-pass filter and wedge filter