Figure 1. Visualization of the two kinds of statistical characteris-
tics that we used to guide the denoising process. (a) The spatial
deviation characteristic obtained by calculating the pixel standard
deviation (SD) within 3 × 3 windows. It reflects the fluctuation
conditions of different spatial positions in the image. (b) The fre-
quencybandcharacteristicobtainedbytheFastFourierTransform
(FFT). Signal and noise are distributed at different frequency band
positions and have different patterns.