[Libreoffice-bugs] [Bug 116861] Minimize Presentation default settings

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=116861

Tomaz Vajngerl <quikee at gmail.com> changed:

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #4 from Tomaz Vajngerl <quikee at gmail.com> ---
Well the values are not percentual, so it is not 25% 50% 75% as the
size/quality factor doesn't increase linearly so you can't say much from the
values itself.

Anyway, value 25 JPEG compression will pretty much destroy your image (bye bye
gradients), 50 is also too low. I would say that the most sensible values are
between 60 - 90. Most people won't see any difference between 75-100, but the
difference in size is big. 
All this also very much depends on the image itself. The assumption here is
that the image is photo, where JPEG makes must sense. For screen images the the
quality factor can get quite different (a lot of edges in the image) and the
most quality killer here is the 4:2:0 subsampling, which we always use (it is
possible to use 4:4:4 subsampling but we never do that).

So just for this profiles I would recommend to use a constant quality factor -
maybe 75 or 80 for all uses. The biggest saver here is the downsampling of the
image anyway. I tried a 8MB JPEG picture at 300DPI and 80 QF is already 1MB, at
150DPI we are already in 300kb range and 96DPI <200kb. I would say that's good
enough for most people.

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