[Radiance-general] getting pixel value at x,y

[Greg Ward]

Hi Lars,

The "-o" option of pvalue would usually do the trick, but pcompos  
gobbles up the EXPOSURE= lines in the input, not passing them to  
subsequent programs.  This is why the exposure needs to be "undone"  
before passing the picture through pcompos.

The reason pcompos behaves thus is that it's designed to take  
multiple input images and the combined result won't necessarily have  
the same exposure.  I should have some more intelligent code in there  
for combining the exposure values in case they're all the same, I  
suppose....

-Greg

> From: "Lars O. Grobe" <grobe at gmx.net>
> Date: June 4, 2008 11:30:34 PM PDT
>
>> 	pcomb -o captured.pic \
>> 		| pcompos -x ${box_width} -y ${box_height} - -${left} -${lower} \
>> 		| pvalue -h -H -df | total -if3 -m
>>
>> The initial pcomb command is necessary to apply the exposure values
>> correctly.  If you want luminance (rather than radiance) output, use:
>
> I actually thought that I could use the -o option calling pvalue
> instead. What is the difference between pcomb -o my.pic | pvalue and
> pvalue -o my.pic?
>
> Thank You again, Lars.