[MapServer-dev] Does mapserver support GIF format for WMS / WMTS services?

[Even Rouault]

Le 11/09/2023 à 09:09, Philippe Ghesquiere a écrit :
> Hi Even,
>
> I thought over your answer again during the weekend. You give the 
> right parameters to get a PNG image format; which is fine.
>
> However, I do need to offer a GIF format support in order to be 
> compliant to the "/DGIWG WMS profile"/ (OGC 09-102r3).
> Indeed, requirement #6 says :
>
>     /A DGIWG WMS server shall support the following raster formats for
>     the GetMap operation /
>
>       * /image/png, /
>       * /image/gif, /
>       * /image/jpeg/
>
> Do you have any other advice / ideas?

- Tell DGIWG folks that the world has moved since the 90's and they 
should consider moving on ;-)

- add middleware between client and mapserver to request png8 to 
mapserver and convert it back to gif in the middleware

- probably easier: enhance mapserver to add back gif support


> Sincerely
> Philippe
>
>
>
> On Fri, Sep 8, 2023 at 4:02 PM Philippe Ghesquiere 
> <philippe.ghesquiere at airbus.com> wrote:
>
>     Thanks Even & Seth,
>
>     I will give it a try
>
>     On Fri, Sep 8, 2023 at 3:02 PM Seth G <sethg at geographika.co.uk> wrote:
>
>         I think `WITH_GIF` is only used to read in GIF images (for
>         symbols etc.)?
>
>         As Even wrote GDAL/GIF doesn't seem to work as an
>         OUTPUTFORMAT. I get:
>
>         msDrawMap(): Image handling error. Failed to draw layer named
>         'countries'. msOGRFileNextShape(): OGR error. OGR
>         GetNextFeature() error'd. Check logs
>
>
>         --
>         web:https://geographika.net & https://mapserverstudio.net
>         twitter: @geographika
>
>         On Fri, Sep 8, 2023, at 2:43 PM, Even Rouault wrote:
>>
>>         Philippe,
>>
>>         Le 08/09/2023 à 14:16, Philippe Ghesquiere via MapServer-dev
>>         a écrit :
>>>         Hi all,
>>>         I am a little bit confused with GIF support for WMS/WMTS
>>>         services.
>>>         In several parts of the documentation, it is mentioned that
>>>         GIF support is discarded with the end of the "GD library"
>>>         support.
>>>
>>>         I noticed the compilation option in CMakelists.txt :
>>>         option(WITH_GIF "Enable GIF support (for PIXMAP loading)" ON)
>>>         I do not understand the "for PIXMAP loading" comment.
>>>
>>>         Anyway, our mapserver does not server WMS/WMTS tiles in GIF
>>>         format.
>>>
>>>         So here are my few questions :
>>>
>>>           * is GIF support enabled by default for WMS/WMTS services ?
>>>
>>         no
>>>
>>>           * do I need to add the option : -DWITH_GIF=ON for cmake
>>>             configuration ?
>>>
>>         only to load raster symbols in GIF format
>>>
>>>          *
>>>             do I need to add a specific mapserver configuration, like :
>>>             OUTPUTFORMAT
>>>                NAME "GIF"
>>>                DRIVER GDAL/GIF
>>>                MIMETYPE "image/GIF"
>>>                IMAGEMODE RGB
>>>                EXTENSION "gif"
>>>             END
>>>
>>         I don't think that will work. The GDAL GIF driver already
>>         expects paletted data, not RGB.  And I don't think switching
>>         IMAGEMODE to PC256 would work since that support has
>>         effectively gone.
>>
>>         I believe the only option to get paletted data is to use PNG8
>>         with the AGG/PNG8 driver and MIMETYPE="image/png; mode=8bit"
>>
>>         Even
>>
>>
>>>         Thanks for your help and advices
>>>         Philippe
>>>
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