Hi Leyla,
Assuming this function describes the fall-off as a function of eccentricity
(distance from image center), and the edge of the image is the edge of your
circle corresponding to x==1 in your formula, you could try:
pcomb -e 'sq(x):x*x;r=sqrt(sq(2/xres*x-1)+sq(2/yres*y-1))' \
-e 'sf=-1.28E-12*r^4 + 3.43E-09*r^3 - 3.38E-06*r^2 +1.45E-03*r
+ 7.70E-01' \
-e 'ro=sf*ri(1);go=sf*gi(1);bo=sf*bi(1)' input.hdr >
corrected.hdr
I think I must be misunderstanding your function, though, because it plots as a
(nearly) straight line that increases from 0.7700 at x==0 to 0.7714 at x==1.
This doesn't seem a likely vignetting correction, as it should go down rather
than up, and by a more significant amount.
Best,
-Greg
> From: Leyla Sanati <[email protected]>
> Date: September 21, 2012 8:36:07 AM PDT
>
> Hi,
>
> I am trying to fix vignetting on fish-eye HDR images. I found this post in
> HDRI archive:
>
> http://www.radiance-online.org/pipermail/radiance-general/2010-April/006711.html
>
> I am still confused on how to use pcomb to fix vignetting.
> Can anyone help me wright the pcomb script using the following polynomial
> function:
>
> y = -1.28E -12 * x 4 + 3.43E - 09 * x3 - 3.38E - 06 * x2 +1.45E - 03 * x +
> 7.70E - 01
>
> Thank you,
>
> Leyla Sanati
> Ph.D Candidate
> UW-Milwaukee
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