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OK. In that case it doesn't look like what I thought. The only other thing I can think is that perhaps some of those JPEGs do come out smaller when saved as PNG and LO is doing that to reduce the file size. But that seems unlikely for photos, as you originally said. Maybe someone else here has some ideas...


Ra wrote:
I never insert images as pictures. The JPEG images are only ever used as
backgrounds for frames. I also never open the JPEGs in any picture editing
application and copypaste from there, the images are only ever used as
files from disk.

What I'm doing is precisely this:

File > Insert > Frame... > OK


[right click on the frame created] > Frame... > Background > As: Graphic >
Browse... > [select the JPEG file from disk] > Type: Area > OK

And then repeat, many times, always selecting a different JPEG for the

On Sat, Mar 1, 2014 at 2:04 PM, Mark Bourne <> wrote:

Sure, but how did you then get those images into LibreOffice?

If you use Insert > Picture > From file, LO knows that the file is a JPEG
and probably even copies the file as-is into the ODF file.

If you open the JPEG file in another application (such as an image
editor), then copy from there and paste into LO, in this case LO will only
have the bitmap data copied from the image editor. It will not know about
the original image file nor what type it was, and probably uses its default
format, i.e. PNG, to save that image data within the ODF file.

My suspicion is that, although you saved all the source images as JPEGs,
those which appear as JPEG in the ODF file were inserted by Insert >
Picture > From file, while those which appear as PNG in the ODF file were
opened in another application and copied and pasted into LO Writer.


Ra wrote:

Good guess but sadly no. All the images are first stored as JPEGs. That's
how I know they in fact *are* JPEGs. ;-)

Ra wrote:


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
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.

Just a guess, but if you copy and paste an image from another file, LO
won't know what format it was in originally (all it has is bitmap data
pasted from the clipboard), so will probably use PNG since it is a
format. Maybe those in JPEG format were inserted by Insert > Picture >
file (or similar), while those in PNG format were opened in another
application, copied from there, and then pasted into LO?

   I've been told the ODF specification recommends using PNGs for bitmaps
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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