[Digikam-devel] Speed of new filters

[Julien Narboux]

Gilles Caulier a écrit :
> 2010/2/13 Julien Narboux <jnarboux at narboux.fr>:
>   
>> Gilles,
>>
>> Did you notice the speed of the new threaded filters (hsl for instance)
>> ? it seems to me that they are far slower than they used to be.
>> Did the old implementation computed the preview on the downscaled
>> version of the picture ?
>>     
>
> yes, it is. This is relevant of imageguidewidget to imageregionwidget
> port. If you fit to window preview with imageregionwidget as
> imageguidewidget do, you compute on whole image.
>
> Imageguidewidget use a downscaled version of preview, in fact the
> screen size of widget. This is why it's very fast. But of course
> zoom/pan is not possible here.
>
> Note : with imageregionwidget, the computation is done on visible
> preview area, not always on whole image. If you zoom down on, the
> computation will be done on visible part of image. In this case it's
> fast

Ok Gilles I understand why it is slower.
It would be nice if imageregionwidget had an option such that the 
preview is computed on the visible image (the downscaled version).
Indeed for many filter f, downscale (f (image) ) ~= f (downscale (image)).
I think this would work for all filters which operate locally on pixels.
I did it "by hand" for the vignetting effect but it would be better to 
factorize that in the imageregionwidget.


Julien