Radlak in Poland "Digital Path Approach Despeckle
Filter for Ultrasound Imaging and Video" propose a so-called escaping paths based on traditional digital paths, and also, they extend this concept from the spatial domain (2D) to the spatiotemporal domain (3D) that is designed for multiplicative noise suppression, specifically for ultrasound image and video filtering.
Salt-and-pepper noise was removed using the despeckle
option in ImageJ.
and the Remove Outliers commands under Process [right arrow] Noise can be applied to remove isolated pixels or small pixel groups.
Secondly, the selected area is preprocessed for despeckle
; the despeckle
algorithm of speckle reducing anisotropy diffusion (SRAD)  is used here.
Cheng, "Comparison of despeckle
filters for breast ultrasound images," Circuits, Systems, and Signal Processing, pp.
Based on the detected structure types, the proposed despeckle
method employs a 2D median filter, a 1D Gaussian filter, and a 2D Gaussian filter to suppress speckles and enhance features.
Thus, we propose to despeckle
an SAR image by minimizing the L0-norm of the difference of average of the image.
NC values of extracted watermark are 1 against, Sharpen, Sharpen Edge, Unsharp Mask, Auto Contrast and Equalize attacks, as well as, NC values are 0.9861, 0.9653 respectively, after the despeckle
, gaussian (3%) attacks.
While in  an extensive list of despeckle
filtering algorithms is provided, which includes methods based on linear filtering (first-order statistics, local statistics, etc.), nonlinear filtering (median, linear scaling, etc.), diffusion filtering (anisotropic diffusion, etc.), and wavelet filtering, we also mention that methods following a VST-like approach  can be also an effective alternative.
The methods are - Spatial for high frequency or fine noise, Threshold for light grain, Temporal for heavy or large grain and noise patterns, and Despeckle
for uneven grain and/or noise.
Noise reduction (type, such as despeckle
, Gaussian blur)