[Live-demo] compressing images with pngquant

Angelos Tzotsos gcpp.kalxas at gmail.com
Fri Jun 5 17:16:43 PDT 2015

On 06/05/2015 10:25 PM, Johan Van de Wauw wrote:
> On Thu, Jun 4, 2015 at 8:33 PM, Johan Van de Wauw
> <johan.vandewauw at gmail.com> wrote:
>> Hi all,
>> I've been experimenting with pngquant [1] to reduce the size of our
>> png images in the documentation. This implements a lossy compression
>> method, but all images I tried came out just fine.
>> In total, we could save about 36Mb by using this compression on all
>> files. I believe this is significant enough to do the change for most
>> files, especially since they are accessed also over the web by people
>> reading the quickstart.
>> I prepared a branch which contains the compressed images at:
>> https://github.com/johanvdw/OSGeoLive-doc/tree/compresspng
>> I made a single commit per image, so if we merge we can still roll
>> back specific images easily.
>> In fact, on github, you can watch the images side by side or as a slide over.
> During the meeting last night I proposed fixing only those images
> where the difference was most significant (>50% reduction in size and
> files of at least 32Kb).
> The results are here:
> https://github.com/johanvdw/OSGeoLive-doc/tree/compresspng
> The result can be downloaded as a package from:
> https://launchpad.net/~johanvdw/+archive/ubuntu/osgeolive-docs-compressedpng
> And it can be previewed at:
> http://gisky.be/osgeolive-docs/en/index.html
> In total we save some 34 Mb, most of which is preserved when
> compressing the files.
> Since I did not see any image which is not good I propose to merge this.
> Kind Regards,
> Johan
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First of all, thank you Johan for your excellent work on creating the 
deb packaging for the documentation.

Looking at the demo site, I think that all the images are not scaled 
properly (set to 100%?).
Any idea what is wrong?


Angelos Tzotsos
Remote Sensing Laboratory
National Technical University of Athens

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