Re: [libreoffice-users] Compress images

2014-02-27 23:28 GMT+01:00 Dale Rebgetz <dale.rebgetz@setec.com.au>:

> I too am very familiar with the various third party methods mentioned
> below, but we must try to address the problem from the point of view of the
> OP. He was made aware of a very simple tool in Word that did exactly what
> he wanted. *How* it achieved it appeared to be of no interest. He was
> asking about the possible existence of a similar tool in LO.
>
> Personally I believe LO needs an equivalent tool, because most of the
> people whom we are trying to convert to LO/OO have no knowledge and no
> interest in the round-about methods detailed below. If there was an easy
> method to perform automatic or one-click cropping and resolution reduction
> *after* the document was compiled, why wouldn't that be the preferred
> method for all users, regardless of their competency with other editing
> tools?


Hm. Probably because there is no "obvious" way to do it that would combine:
- ease of use
- efficiency in all case
- low development cost

I don't know how often this feature is requested for odt files. I know that
for pdf you can set parameters for the image compression, and it make sense
since the resulting file is unlikely to undergo future changes, but it's
less obvious for file formats that are not at the "end" of the editing
line. It's probably better to work with the "highest" resolution needed,
and produce smaller files as needed. Hmm.

As a "proof of concept", I put together a java program that take an odt
file as input. You can then set the "requested" DPI and jpeg quality, and
save. At this point, every pictures that are larger than needed (that's why
we need DPI) are resized, and all pictures are compressed using either jpg
or png, whichever gives the smalles size. Something as simple as that
already have issues, like when there's transparency involved.
Also, it's only tested on a few files (including
https://wiki.documentfoundation.org/images/9/96/WG40-WriterGuideLO.odt for
funsies).

If anyone want to give it a try here's the jar. It's highly unlikely to
corrupt your source file (the source file is never ever written), but
there's also no guarantee that the output will work ;)
<http://cleyfaye.net/share/odtcompress.jar>
For example, on the writer guide linked before, it goes from 13MB to 9MB
with default settings. Of course it's not the best example: all pictures
are already reasonably sized, and it's mostly screenshots so the quality
drop is very noticeable...

Anyway, if anyone want to look at the source code (without reversing the
jar :D) I'll provide them. But know that it's mostly an ugly hack just to
see how well it would work :)

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