This is documentation for Mathematica 7, which was
based on an earlier version of the Wolfram Language.

# EntropyFilter

 EntropyFilter[image, r]filters image by replacing every value by the information entropy of the values in its range r neighborhood. EntropyFilter[data, r]applies entropy filtering to an array of data.
• EntropyFilter[image, r] computes the information entropy of the values in (2r+1)×(2r+1) blocks centered on each pixel.
• Given a set of values pi, the information entropy is taken to be .
• At the edges of an image, EntropyFilter uses smaller neighborhoods.
• EntropyFilter[image, {r1, r2}] uses neighborhoods with vertical range r1 and horizontal range r2.
• In EntropyFilter[data, ...], data can be an array of any rank, and can contain symbolic as well as numerical entries.
Entropy filtering of random disks:
Apply entropy filtering to show areas of higher information content with higher intensities:
Apply an entropy filter to a vector of numbers:
Entropy filtering of random disks:

Apply entropy filtering to show areas of higher information content with higher intensities:
 Out[1]=

Apply an entropy filter to a vector of numbers:
 Out[1]=
 Applications   (1)
Entropy filtering can reveal JPEG compression artefacts:
New in 7