[HDRI] ximage and hdri

[Giulio]

low teck approach, just command line:
I would just generate a mask with photoshop, an image with just white  
and black pixels, but in RGB.
convert it to tiff and then to pic    (ra_tiff -r ).
use pcomb with image 1 and image 2 and write an expression that takes  
value of pixels in your HDR only if they are inside of the mask, all  
the others null (basically multiply image 1 by image 2, check that the  
mask contains 0 and 1 only!).
use pvalue on the filtered image and convert to numbers
use total and get the sum of all data from filtered image, TL
count the white pixels in the mask (pvalue and total for example), TN
TL/TN = average luminance within the mask
....
the whole thing can be written in a script.
and perhaps also put together with a nice sequence of pipes.
G


On 1 Jun 2009, at 21:29, Roberto Rodriguez wrote:

> I´m a PhD student from Argentina, member of a research team  
> advocated to
> the study of natural lighting. We are exploring the HRDI technique  
> and we
> found a limitation while using hdrgen and ximage: Only squared  
> shapes are
> avaiable to average Luminances, and we need to calculate the mean
> Luminances for radial shapes (circular, toroidal) in order to get the
> luminance contrast in the field of view.
>
> How can we overcome this? Can we "borrow" the source code of ximage  
> so we
> can write a script acording to our needs?
> Thank you.
>
> -- 
> Dis. Ind. Roberto G. Rodriguez
> Laboratorio de Ambiente
> Humano y Vivienda-LAHV
> INCIHUSA-CRICYT-CONICET
> Av. Ruiz Leal s/n, Pque. Gral. San Martín
> (5500) Mendoza, Argentina
> Tel. 54-261-5244334
> Fax: 54-261-4287370
> rgrodriguez at mendoza-conicet.gov.ar
> http:www.cricyt.edu.ar
>
>
>
>
> -- 
> Dis. Ind. Roberto G. Rodriguez
> Laboratorio de Ambiente
> Humano y Vivienda-LAHV
> INCIHUSA-CRICYT-CONICET
> Av. Ruiz Leal s/n, Pque. Gral. San Martín
> (5500) Mendoza, Argentina
> Tel. 54-261-5244334
> Fax: 54-261-4287370
> rgrodriguez at mendoza-conicet.gov.ar
> http:www.cricyt.edu.ar
>
>
>
>
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