[Radiance-general] Re: calculating percentages of a given value in a radiance .pic

[Greg Ward]

And here is one of the many possible standard Radiance tools ways:

pvalue -h -H -o -b -df input.pic | rcalc -if -of -e '$1=1;$2=if(179* 
$1-THRESHOLD,1,0)' | total -if2

You need to set THRESHOLD to the desired luminance value (in cd/ 
m^2).  This will give you two numbers, the ratio of which is the  
percentage you seek.  If you want to do it all on the command line,  
you can add:

	| rcalc -e '$1=100*$2/$1'

to the end of the pipe.

Best,
-Greg

> From: "Marija Velickovic" <maricanis at gmail.com>
> Date: October 20, 2008 3:42:28 AM PDT
>
> Hi,
>
> I suppose you can use some of standard Radiance tools for that, but  
> here is another way we use.
>
> In Raddisplay http://deluminaelab.com/en/raddisplay_details.html  
> program you can create falsecolor image from your original radiance  
> image. If you define false color palette with 2 colors - one has  
> value 0 and another value you want to use as a threshold, and open  
> Statistiques dialog, you'll have  percent for each color in the  
> tablle. You can also define the palette with more colors, for  
> various threshold values.
>
> Hope this helps,
> Marija
> De Luminae.
>
> 2008/10/20 Galen Burrell <galenburrell at yahoo.com>
> Hi All,
> I have a radiance .pic with lux values calculated using rpict -i.   
> Is there a way to calculate the percentage of the pixels that are  
> at or above a specified value?
> Thanks,
> Galen
>