[Qgis-developer] QGIS Server - WMS GetMap Jpeg compression

Marco Hugentobler marco.hugentobler at sourcepole.ch
Mon May 26 08:12:39 PDT 2014

Hi Michael

At the moment, the compression rate is left to the Qt library both for 
png and jpeg (-1 is given to QImage::save). I agree it will be usefull 
to change from client or from project.

 >Why not
 >FORMAT=image%2Fjpeg%3B compression%3D90
 >I guess it is not standard ?

The problem here is that there has to be a new parameter for each 
compression rate. It might be better to have the possibility to 
configure the image quality in the project or by giving an optional 
parameter for the image quality (0-100 as the Qt parameter). So if the 
parameter is not there, the project setting is used. And if the setting 
is not set, -1 is used as it is now.


On 23.05.2014 18:44, kimaidou wrote:
> Or even better, having it layer per layer. Like we do for png , for 
> example
> FORMAT=image%2Fpng%3B mode%3D8bit  -> image 8 bits
> Why not
> FORMAT=image%2Fjpeg%3B compression%3D90
> I guess it is not standard ?
> 2014-05-23 18:36 GMT+02:00 Paolo Cavallini <cavallini at faunalia.it 
> <mailto:cavallini at faunalia.it>>:
>     Or even better, having a config at runtime, project by project.
>     On 23 maggio 2014 18:33:00 CEST, kimaidou <kimaidou at gmail.com
>     <mailto:kimaidou at gmail.com>> wrote:
>         Hi devs, Marco, René-Luc,
>         I have some people giving feedback about the current JPEG
>         compression. Many users think the "FORMAT=image/jpeg"
>         parameters in the GetMap requests produce poor quality images.
>         I guess the "80%"  rate is used. I think it could be enough to
>         increase it to 90 to produce better looking images (I
>         personaly create my pyramid with this option with gdal), or
>         better to leave the choice when installing QGIS Server by
>         using a config parameter.
>         Any feedback welcome
>         Michael
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Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee

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