[Radiance-general] aspect ratio problem

[iebele]

Hi Lars,

Thanks for your suggestion using image aspect ratios instead of pixel 
aspect ratios.

Anamorpic Pal is (as I understood) a 720x576 image stretched to 1024x576 
by the displaying device.
This suggests a pixel of which width is 1.42 taller as its height.

I tried your suggestion and rendered my image at 1024x576 square pixel 
with a the vv value calcualted like this:
vv = vh / 1.42  (where 1.42 is 1024/720 )

Rendering square pixels at 1024x576 works fine, at least the image fits 
the videoframe.
But I really wonder if the way I calculated the vv value is correct.

-Iebele


Lars O. Grobe wrote:

>> I render for PAL anamorphic ( 16:9 - 720x576 ) video.
>> I use option -pa 1.42  in both rpict and pfilt for setting the proper 
>> aspect ratio. The output resolution is 720x576.
>> The resulting image indicates (using getinfo) an aspect ratio 1.42 as 
>> expected.
>> But  the result of a radiance image converted using ra_tiff  seems to 
>> be a tiff file with square pixels (aspect ration 1:1).
>
>
> I think you should not use -pa at all (or at zero). You can use it if 
> one pixel is not like a "square", to correct. But in your case, the 
> pixels have an aspect ratio of about 1/1, so the -pa setting results 
> in a picture stretched just as far as to get a square picture. In 
> other words: the aspect ratio of the image is determined by vv and vh 
> (or the resolution), the pa setting is for the pixel aspect ratio. 
> That is at least how I understood -pa....
>
> CU Lars.
>
>
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