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| File Edit Options Process Analyze Video Macros Stacks SEM SPM Windows Help |
Sharpen Shadow Find Edges Rank Filters Dither Convolve PlugIn Filters
Enhance Contrast Equalize Fix Colors Differential Curvature Unsharp Mask Hough Transform |
These filters,
with the exception of Reduce Noise and Dither, are implemented using 3 x 3 spatial
convolutions, where the value of each pixel in the selection is
replaced with the weighted average of its 3 x 3 neighborhood. They are
not limited to rectangular selections. The entire image is filtered if
no selection is active. They do not work correctly with 8-bit true
color images. They can be aborted by typing command-period. The 3 x 3
tables shown below are the coefficients (weighting factors) for the
filters.
Find Edges performs a Sobel edge
detection operation. Two convolutions are done using the kernels shown
below, generating vertical and horizontal derivatives. The results are
then combined by using the square root of the sum of the squares of the
two derivatives.
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Steve Barrett November 2014 |
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