On mardi 17 décembre 2019 07:42:32 CET Jochen Keil wrote:
(...)
> 
> Btw. does anybody know how darktable handles editing of pictures? E.g. my
> pictures are 8000x4000, yet my viewport has only 2000x1000 (just an
> example). Shouldn't it be enough to render the image to this size to
> improve editing speed?
The numbers that have been given so far were for export, presumably to full 
size. Does rendering take as long as exporting the images?
According to the manual, full demosaicing for viewport is only done when the 
image is zoomed at more than 50%, or when asked for explicitly by the user 
(through a setting in the preference dialog).
> Also, I noticed that by enabling the amaze demosaicing the editing
> performance degrades. That's why I usually switch it to amaze at the end of
> my editing process. However, from what I understand demosaic is one of the
> first (if not the first) module in the pipeline. Shouldn't it be possible
> to cache the result, just like exporting to a tiff and reloading?
> 
"Amaze" is known to be a slow method, which is why it's not the default.
Demosaic is not the first step in the pipeline, at least 'raw black/white 
point',  'white balance' and 'highlight reconstruction' come before. And those 
are almost always present. As under normal operation (with normal screen 
sizes)  demosaicing is *only* performed when zoomed in, or on export, caching 
of the demosaicing step isn't all that useful (I think).

A proper cache might also be quite complicated to implement correctly: there 
are other slow modules, which would also benefit (e.g. 'denoise (profiled)'). 
But then you have to have multiple intermediate results cached (after each 
expensive step), or keep track of which change in the processing stack 
invalidates the cache in each particular case.

> The export to tiff & reload "pattern" does help performance-wise, but I
> don't like it, because you'll scatter your history across several files.
Perhaps check your 'preferences' setting wrt demosaicing (core options, 
'demosaicing for zoomed out darkroom mode'). If it's set to "full (possibly 
slow)", try one of the other options? (That should have no effect on the 
*exported* results).

And what happens if you aply a style with (just) the "amaze" demosaicing on 
export, while having the default active during editing? Or is there a 
particular reason you need to have the final demosaicing active while editing?

Remco


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