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Accurate
Image Manipulation for Desktops
Sharpen 7-band (1st, September,
1999)
Description
Powerful sharpening
filter, effect is controllable over 7 tonal bands. It utilizes the popular
unsharp mask over 3x3 kernel (the same as radius 0.5 in Photoshop). The
possibility to adjust the sharpening amount over the 7-bands provides far
better quality than a simple threshold cut.
Selection Dropdown
First tell the filter
what kind of image you are editing: Low Key Image, Middle
Key Image or High Key Image. These affect slightly
to the division of the bands. If the "1/7 tone" slider responds too strongly
set selection to Low Key Image if the "1/7 tone" slider responds
too slightly set selection to High Key Image.
Check Boxes
0/255 Inv
This is a preview
function only. When enabled it will give visual feedback for pixels that
have channel value 0 or 255. This greatly helps in applying the amount
properly. To see the effect slowly enable/disable the 0/255 Inv
check-box.
Sliders
Amount,
0...500.
the initial amount of the sharpening. 500 is approximately equal to Photoshop
USM at amount=500, radius=0 and threshold=0.
n/7 tone, these
7 slider affect to seven perceptually equal ranges, 1/7 tone is
the most dark range and 7/7 tone is the brightest range.
The value of these sliders is percentage from Amount, ranging
from 0 too 400%, with default value 100. Note that setting a slider to
0 completely disables sharpening for that range and setting it to 400 will
multiply the sharpening amount by 4 for that range. (The spline that
the x/7 tone sliders control is smoothed slightly).
Notes
This filter is not
very usable in gamma spaces since the two or three lowest sliders (in the
black-end of the range) do not notably affect to gamma images. This is
not the problem of the filter but is due to the image-gamma. It is possible
to write the filter in such way that it 1) removes the gamma compensation,
then 2) applies the sharpening and finally 3) re-applies the image-gamma.
Since the filter works in 31-bit/color this does not degrade the quality
but it makes the filter extremely slow. It is already a little slow because
of all the calculation needed.
Please note that the sliders
are strong.
First thing to do when the
filter opens is to Shift-Click the preview + button in order to have the
1:1 zoom in the preview box. Then drag the image so that a representative
area is shown, the dragging is not limited to the preview box boundaries.
Author
Timo Autiokari.
Homepage:
Accurate
Image Manipulation for Desktops
Usage and Distribution Rights
Free to download
and use, all re-distribution prohibited.
Filter Engine
FilterFormula v
1.1, by
ATS/Graphics
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