Re: [boost] Promote Traits -- Review of Generic Image Library (GIL)

From: koethe_at_[hidden]
Date: 2006-10-16 06:33:17

Quoting Lubomir Bourdev <lbourdev_at_[hidden]>:
> Promotion traits, as I stated in another thread, are handy and there  
>  is definitely a value in providing them. But I think they are an   
> integral part of the imaging algorithms and therefore belong in the   
> numeric extension. So stay tuned!
>

I my experience promotion traits are absolutely necessary to implement  
genereric image processing algorithms. Consider the simple matter of  
adding two or more byte images. In order to avoid overflow,  
intermediate results should be stored in a short or an int. If the  
result is to be written back to a byte image, the destination accessor  
can take care of shifting the result back into the appropriate range  
or clipping at the range limits. Promotion traits control this  
behavior. Hardly any algorithm in VIGRA can do without them.

Regards
Ulli