Fig. 21.

(a) Sample local mean distribution of the image without noise (solid-bold) and with noise (dashed), with σ_n = 10. (b) Normalized distribution of $\sqrt{2/\pi }\langle I_{i,j}\rangle$ of the noisy image with σ_n = 10. Window size: 3 × 3 (dashed), 7 × 7 (solid), 11 × 11 (dash–dotted) and 21 × 21 (dotted).