1. An image denoising method of removing a noise from an image captured by an image sensor, the image denoising method comprising the steps of: sequentially selecting a pixel in the image captured by the image sensor as a current pixel, wherein pixels in the image around the current pixel are defined as neighborhood pixels of the current pixel; dynamically determining a current search block enclosing the current pixel and a strength parameter for defining an image denoising strength according to complexity of the same image around the current pixel; determining a comparison block for each of the pixels in the current search block of the same image, wherein the comparison block encloses the each of the pixels; transforming the comparison block for each of the pixels in the current search block of the same image to a frequency domain to form a frequency-domain comparison block; determining a current frequency basis for the frequency-domain comparison blocks of the same image; obtaining a similarity between each of the neighborhood pixels and the current pixel in the current search block according to the current frequency basis of the same image; determining, for each of the neighborhood pixels, a weighting related to the current pixel according to the strength parameter, the similarity and a distance between each of the neighborhood pixels and the current pixel in the current search block of the same image; and performing a weighted averaging for the neighborhood pixels and the current pixel in the current search block according to the weightings to obtain a reconstruction value of the current pixel of the same image, wherein a number of comparison blocks is same as a number of pixels in the current search block of the same image, and the current search block and the comparison block for each of the pixels in the current search block of the same image are at least partially overlapped with each other.