Proposal: Add thumbnails of different sizes to .kra files?

[Alvin Wong]

Hi,

I would like to suggest Krita add (uncropped) thumbnail images of
different sizes to the file to allow faster extraction of thumbnails
by external applications.

There is currently one preview.png which is at maximum 256x256, so
generating thumbnails larger than that would require scaling down from
the mergedimage.png which could be very large and may take a
comparatively long time to process. Even though the actual time per
file might not be much, it could add up for a lot of files.. Also, the
preview.png is cropped to the non-transparent region
(https://bugs.kde.org/show_bug.cgi?id=363968) which makes things a bit
weird and inconsistent.

I think having thumbnails for the sizes (maintaining aspect ratio) of
256x256 and 1024x1024 would suffice, but boud suggested having 512x512
might be nice too. Adding in these sizes means that, for thumbnails
equal to or below the available sizes, they can be extracted and
optionally scaled down from those instead of scaling down from the
mergedimage.png. Obviously, sizes larger than that would still require
using the mergedimage.png, but hopefully it would be quite rare for an
application to request for thumbnails larger than 1024x1024... (4K
displays aren't popular yet... right?)

For the record, according to this MSDN page
(https://msdn.microsoft.com/en-us/library/windows/desktop/cc144118(v=vs.85).aspx)
Windows asks for the sizes 32/96/256/1024.

I am asking for this as the developer of the Windows Shell Extension.

Any suggestions?

Best Regards,

Alvin