[mapserver-dev] MapServer tutorial - symbology

[Rahkonen Jukka (MML)]

Hi,

I think that this kind of discussion belongs to mapserver-users (cc:ed). I hope that developers read also the users mailing list, and users may have more to say about what they consider hard with styles. Also, Mapserver users learn from reading mails like this, and that there are mails on the list at all proves that the project is not dead. Developers can discuss on the dev list or in GitHub about how to implement the “size by expression” with C++ and so on.

One thing that always feels odd to me is that why we do not have any default style for points but we must especially define some symbol in the mapfile. I have been thinking that perhaps we could have internal, hard coded symbols at least for these 6 which are defined in the SLD standard:

“The WellKnownName element gives the well-known name of the shape of the mark. Allowed values include at least “square”, “circle”, “triangle”, “star”, “cross”, and “x”, though map servers may draw a different symbol instead if they don't have a shape for all of these. The default WellKnownName is “square”. Renderings of these marks may be made solid or hollow depending on Fill and Stroke elements. These elements are discussed in Subclauses 11.2.2 and 11.1.3, respectively.”

If user gives no symbol in the mapfile for points it would mean “square”. If symbol with the same name than WellKnownName is defined in mapfile or in symbolset it would override the standard symbol. If there is a special need for non-visible points  we could have one more: SYMBOL “NONE”.

-Jukka Rahkonen-

Lähettäjä: mapserver-dev [mailto:mapserver-dev-bounces at lists.osgeo.org] Puolesta Seth G
Lähetetty: 25. lokakuuta 2016 13:20
Vastaanottaja: mapserver-dev at lists.osgeo.org
Aihe: [mapserver-dev] MapServer tutorial - symbology


Hi all,

I have updated the second quick start tutorial on SYMBOLS and symbolizing data. A draft page is available at: https://geographika.github.io/tutorial/quickstart/symbolizing.html

I ran through this with around 6 people, and a few questions came up. If anyone can provide details that would be very helpful. Also comments/improvements on the tutorials are very welcome.

1. Are there any performance or other benefits of VECTOR symbols over IMAGE/SVG? (Although I think SVG is currently not available in ms4w - http://www.ms4w.com/trac/ticket/3 ). The manual entering of coordinate details seems pretty difficult compared to using/making SVGs.

2. At the top of the http://mapserver.org/mapfile/style.html#style page there is the sentence "The final intent is to have named styles (Not yet supported) that will be re-usable through the mapfile." I presume this means there was a plan to use STYLES similar to a SYMBOLSET? Are there still any plans to do this?

3. I was looking to create circle symbols of different sizes based on an attribute, using one of the datasets from Natural Earth. The cities with large populations has a smaller "RANK_MAX" - so the size needs to be inverse to an attribute. There does not appear to be any easy way to do this without modifying the data.  You can set the size using an attribute e.g. "SIZE [MYHEIGHT]" but is there a good reason why a MapServer expression couldn't be used here? I can add as a feature request to GitHub if it could be a nice addition.

A final question - should I post these emails to the dev or users MapServers lists?

Regards,

Seth
--
web: http://geographika.co.uk
twitter: @geographika
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