An image noise reduction method in frequency domain is provided,
comprising selecting a first image and applying a Fourier transform
thereon to acquire a first frequency spectrum, wherein each pixel of the
first frequency spectrum has a real part X and a imaginary part Y,
calculating a first energy of each pixel and a first mean energy of all
first energies of the pixels, calculating a first mean value and a first
standard deviation of the real part of the pixels, calculating a second
mean value and a second standard deviation of the imaginary part of the
pixels, determining a first and a second predetermined values, when the
first energy exceeds the first mean energy, the first and second
predetermined value are replaced with X and Y, and when the first energy
does not exceed the first mean energy, X and the Y are reserved.