Re: [E-devel] Prototype thumbnailer now has a Epeg plugin (fwd)

[Jose G. <jos...@ju...>]

>>  
>>>> Scaling to the nearest power-of-2 is certainly asking for horrible
>>>> resuls. I also don't think the hardware acceleration will buy you 
>>>> much,
>>>> transferr overhead is quite high and not-so-current hardware is huge
>>>> limitations on maximum sizes it can handle. E.g. the given example
>>>> wouldn't work with most IGD chips.
>>>>
>>>>         
>>>    Power-of-2 *fraction*, ie. 1/2, 1/4, etc. of the original size.
>>>     
>>
>> Sure, but at least if you use any type of non-trivial interpolation
>> algorithm to compute the final non-power-of-2-fraction, you get inferior
>> results if you cut down to the next  larger power-of-2-fraction first.
>> Consider you want to scale down from 64 pixel to 31 pixel -- you throw a
>> lot of information away by scaling down to 32 pixel first, even though
>> that is cheap.
>>   
>
>   The semantics isn't entirely up for grabs. Either we choose the nearest
> power-of-2 fraction which is greater than the desired, or nearest period.
> Usually, for this application one would take the former (though at the
> moment I don't recall what Carsten threw in there), and in your example
> that would mean no jpg-scaling and simply software down-scale to 31.
>
>

   Errr..  I mean in your example one *would* jpg-downscale to 32,
and the software down-scale to 31. The result, with 'smooth-scaling'
would be quite good.

     Need to take Gustavo's 12 hr. advice... :)
 
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