[SOLVED]Windows script driving IM: basic arithmetic on param

[NicolasRobidoux]

Bart van der Wolf, with some assistance from Fred Weinhaus, Alan Gibson and myself, has been polishing a Windows script that combines several ImageMagick commands to produce excellent quality when resizing. (Right now, it only works "perfectly" with sRGB input and output, but this may be extended to other input color spaces later.)
This script: http://www.luminous-landscape.com/forum ... #msg748602.
Now, we would like to be able have the script take an input value (let's call it sharpAmount, for sharpening amount), between 0 and 100, and perform some arithmetic on it in order to pass a derived value, named deblurValue, to -define filter:blur=deblurValue.
Specifically, we would like the relationship between the input and derived value to be as follows:

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deblurValue = 0.88549061701764 + (1 - .01*SharpAmount)*(1-0.88549061701764)

(Of course the expression on the right can be simplified a bit. This is besides the point.)
Does anybody know how to do this (in Windows)?
Link to original question: http://www.luminous-landscape.com/forum ... #msg748960

[snibgo]

In a Windows BAT script, I would do it like this:

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set SharpAmount=34.56

for /f "usebackq" %%L in (`identify ^
  -format "deblurValue=%%[fx:0.88549061701764 + (1 - .01*%SharpAmount%)*(1-0.88549061701764)]" ^
  xc:`) do set %%L

echo %deblurValue%

Note there are two back-quote characters.

We can do multiple calculations in one go:

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for /f "usebackq" %%L in (`%IM%identify ^
  -format "X=%%[fx:1/2]\nY=%%[fx:2/3]" ^
  xc:`) do set %%L

See my pages for many similar examples.

[NicolasRobidoux]

Alan: \o/

[snibgo]

Bart's sample...

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>SET Deblur=100

>SET Deblur=convert xc: -format '%[fx:1-3290*%Deblur%/2873127]' info:

>%deblur%
'0.885491'

...assigns a long string, starting with "convert" to Deblur. That string is a command. So when he executes it as a command, the command runs, and convert runs, returning the value between the required single-quote characters. But it is useless in other contexts.

[NicolasRobidoux]

http://www.luminous-landscape.com/forum ... #msg749071

[snibgo]

Sorry, I'm not a member of that forum.

The only concern I have is that the precision is limited to only a few significant digits.

For greater precision from IM, insert "-precision 9" or whatever before "-format".