[Radiance-general] pvalue output

[kkonis at berkeley.edu]

Hello all,

I am looking at the output from

pvalue -o -b A.hdr > test.txt

and checking to see if the luminance from the pvalue output for a given
pixel matches the luminance for the same pixel when clicked on in
Photosphere. (I am doing this to create a powerpoint slide that
illustrates that luminance can be extracted from each pixel in a radiance
image for a very general audience).

(Actually i click a pixel on the image in Photosphere and then track down
it's record in the pvalue output)

I noticed that the 0,0 Origin in Photosphere is the upper left corner, and
for Radiance images it is the lower left (i believe ? ).

Since my image is 1536 x 1536 pixels, pixel x=256,y=550 in Photosphere is
then row:

x=256, y=abs(550 - 1536), brightness.value

 . . . . as output from Pvalue.

I take brightness.value*179 to get my pixel luminance and it matches
closely with the output from Photosphere, but not exactly. I want to ask
if I am using the correct conversion from pvalue's output to luminance,
and that my understanding of the (0,0) origin locations in Radiance and
Photosphere is correct.


I'm a relatively new user so any help would be appreciated!

Kyle

******************************************
Kyle Konis
PhD Student
Lawrence Berkeley National Lab (LBNL)
UC Berkeley Center for the Built Environment (CBE)
206.303.9786
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