I am planning to show some Image Processing
research results on which the final step
is a sharpening operation:

   convert -sharpen '0.0x0.5' in.png out.png

In case I'm asked, what, precisely, does "convert" use
for sharpening?

My guess, without looking into the Source Code, is that it is using an
un-sharp mask.  Maybe one of the developers could give me the correct
answer.

If it is an unsharp mask, what type of low-pass filter is the mask?
I'm guessing a Gaussian, since within `display' the "sharpen"
function requests two parameters:  

"sharpening radius" x "standard deviation".

The latter parameter suggests a Gaussian.

By the way, when I vary the "sharpening radius" I see no difference in
output.  The "standard deviation" controls the amount of sharpening
performed.  Why is this?


Any answers to my questions will be much appreciated.
Thanks.

Dean S. Messing
Sr. Scientist
Display Algorithms & Visual Optimization Lab
Information Systems Technologies Dept.
Sharp Laboratories of America

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