Filters (Spatial): Unsharp Mask
When applied to an image, this algorithm produces a sharpened version of the image or the image volume defined by a VOI of the image.
The sharpening process works by utilizing a lowpass filtered (blurred) version of the original image. This is then subtracted away from the original to detect the presence of edges, creating the unsharp mask (effectively a highpass filter). Contrast is then selectively increased along these edges using this mask — leaving behind a sharper final image.
The effect of a highpass filter, like the unsharp mask technique, is to enhance sharp intensity transitions (i.e., edges) but at the cost of enhancing noise.
Image types
You can apply this algorithm to all image data types, except complex and RGB images, and to 2D, 2.5D, 3D, and 4D images.
Applying the algorithm
To run this algorithm, complete the following steps:
 Select Algorithms > Filter (spatial) > Unsharp mask. The Unsharp Mask dialog box (Figure 1) opens.
 Complete the information in the dialog box.
 Click OK.
 The algorithm begins to run, and a popup window appears with the status. The following message appears
 "Unsharp Masking Image."
 When the algorithm finishes running, the popup window closes, and the results either appear in a new window or replace the image to which the algorithm was applied.
X Dimension

Specifies the standard deviation (SD) of Gaussian in the X direction.


Y Dimension

Specifies the SD of Gaussian in the Y direction.
 
Z Dimension

Specifies the SD of Gaussian in the Z direction.
 
Use image resolutions to normalize Z scale

Normalizes the Gaussian to compensate for the difference if the voxel resolution is less between slides than the voxel resolution inplaine. This option is selected by default.
 
Process each slice independently (2.5D)

Filters each slice of the dataset independently of adjacent slices.
 
Image  (k<1) * blurred image

Determines the amount of filtering, or sharpening, applied to the edges of the image or a VOI of the image. Low values sharpen image edges but increase noise. The default value is 0.75.
 
New image

Shows the results of the algorithm in a new image window.
 
Replace image

Replaces the current active image with the results of the algorithm.
 
Whole image

Applies the algorithm to the whole image.
 
VOI region(s)

Applies the algorithm to the volumes (regions) delineated by the VOIs.
 
OK

Applies the algorithm according to the specifications in this dialog box.
 
Cancel

Disregards any changes that you made in this dialog box and closes the dialog box.
 
Help

Displays online help for this dialog box.

See also:
 Filters (Spatial): Adaptive Noise Reduction
 Filters (Frequency)
 Filters (Spatial): Adaptive Path Smooth
 Filters (Spatial) Anisotropic Diffusion
 Filters (Spatial): CoherenceEnhancing Diffusion
 Filters (Spatial): Gaussian Blur
 Filters (Spatial): Gradient Magnitude
 Filters (Spatial): Haralick Texture
 Filters (Spatial) Laplacian
 Filters (Spatial): Local Normalization
 Filters (Spatial): Mean
 Filters (Spatial): Median
 Filters (Spatial): Mode
 Filters (Spatial): Nonmaximum Suppression
 Nonlinear Noise Reduction
 Filters (Spatial): Regularized Isotropic (Nonlinear) Diffusion
 Filters (Spatial): Slice Averaging