[Sidefx-houdini-list] OT: sRGB to linear question

Edward Lam edward at sidefx.com
Tue Jul 8 14:09:23 EDT 2008


Ivan DeWolf wrote:
> interesting... I tested this, scaling the dali lama image in Houdini and Nuke.
> Houdini's compositor did get it wrong, but nuke nailed it. the image looked way
> meffed up in the GUI if you zoomed in and out on it. 

Houdini's compositor doesn't apply gamma correction (or "uncorrection"). 
It doesn't make any assumptions about the image data being read in. Thus 
you would need to convert it to 16-bit and then to linear (via the Gamma 
COP) before scaling.

-Edward

> Quoting Edward Lam <edward at sidefx.com>:
> 
>> sRGB is NOT any worst or less accurate. It's what you might do with the 
>> non-linear image that *might* be a problem. For a striking example of 
>> what can go wrong if you perform image algorithms that assume linear 
>> space with non-linear images, see this link:
>>     http://www.4p8.com/eric.brasseur/gamma.html [1]
>>
>> As usual, it's only a problem if you don't know what you're doing. :)
>>
>> Cheers,
>> -Edward
>>
>> 1. Note that (AFAICT) the author of the link doesn't try properly gamma 
>> calibrate the software he tests.
> 
> 
> 
> -Ivan
> 
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