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I have noticed some unexpected (and possibly inconsistent) behavior of
documents producet with LO Writer. Here's my scenario: I have several
frames in the document and each of them has a JPEG photo as the background.
Each frame has a different image as a background. There are no other
graphics in the document, just some text. The resulting document ends up
being considerably larger than the sum of all the images and all the text
content put together.

Knowing that ODFs are really just ZIP archives, I decided to dig a little
deeper. Having opened an ODF file with an archiver I noticed most (but not
all, surprisingly!) of my JPEGs got converted to PNGs before getting
stored. I don't know much about this but up until now I believed LO stores
all external images as direct file copies, or at the very least in the
original format, so this striked me as odd.

I've been told the ODF specification recommends using PNGs for bitmaps and
SVG for vector graphics. This makes sense generally but is also quite
inefficient for photos as PNG photos tend to be much larger than JPEGs. It
is also weird that only some of my images got converted.

Anybody know and can explain the logic behind this? My document currently
contains about 100 such images, the JPEGs are all together about ~15MB in
size, the rest of the document is mostly plain text with some formatting,
and yet my document ends up at about ~47MB. I would like to optimize and
reduce this if possible.

In case it matters, the document was produced over several weeks in LO 4.x
or newer on Windows (XP/x86 and 7/x64) and Linux (x86).

Thank you.

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