[MapServer-users] Changing opacity of one layer in a multilayer WMS request URL with MapServer 8

[Rahkonen Jukka]

Hi,

About the SLD, opacity appears in stroke, fill, graphic, and raster in SLD 1.0.

-Jukka Rahkonen-

Lähettäjä: MapServer-users <mapserver-users-bounces at lists.osgeo.org> Puolesta Steve Lime
Lähetetty: keskiviikko 22. helmikuuta 2023 17.47
Vastaanottaja: Matthew Graber <grabermtw at gmail.com>
Kopio: mapserver-users at lists.osgeo.org
Aihe: Re: [MapServer-users] Changing opacity of one layer in a multilayer WMS request URL with MapServer 8

Hi Matthew: That functionality was indeed removed as part of 8.0. I kind of expect that we might build back something for more limited use cases if necessary, Does SLD support opacity/transparency?

--Steve


On Tue, Feb 21, 2023 at 10:52 AM Matthew Graber <grabermtw at gmail.com<mailto:grabermtw at gmail.com>> wrote:
Hello all!

With MapServer 8, I'm wondering what the proper way to change the opacity of a single layer in a multilayer WMS request is.

For example, the following URL excerpt shows the old way of accomplishing this that worked while using MapServer 7:

SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng&LAYERS=test_a,test_b&map.layer[test_b]=OPACITY+50

My understanding is that this would have the same effect as adding "OPACITY 50" to the test_b layer in the mapfile. The mapfile containing test_a and test_b did not have OPACITY included when they were written. Obviously, this no longer works with MapServer 8, and now that request has the same results as omitting the "&map.layer[test_b]=OPACITY+50" portion entirely.

Based on https://mapserver.org/fr/MIGRATION_GUIDE.html<https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmapserver.org%2Ffr%2FMIGRATION_GUIDE.html&data=05%7C01%7Cjukka.rahkonen%40maanmittauslaitos.fi%7C751680624f65498df41008db14ec07c5%7Cc4f8a63255804a1c92371d5a571b71fa%7C0%7C1%7C638126776216198394%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=CbH%2FfRUQdX9uq8H9QRy48X0BggqTStn4IDQR4jD%2B97Y%3D&reserved=0>, I see that OPACITY now belongs inside a COMPOSITE object. I tried the following modifications to the request URL:

SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng&LAYERS=test_a,test_b&map.layer[test_b].composite=OPACITY+50
SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng&LAYERS=test_a,test_b&map.layer[test_b].composite[0]=OPACITY+50

I also tried this both with the mapfile left as-is, and with an empty COMPOSITE object being included in each layer object, and each time I got the same unsuccessful result as before.

Is there a way to accomplish this in MapServer 8?

Also, does this map.layer[layername]=... syntax still work in MapServer 8? The documentation at https://mapserver.org/cgi/controls.html#using-mapserver-version-8<https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmapserver.org%2Fcgi%2Fcontrols.html%23using-mapserver-version-8&data=05%7C01%7Cjukka.rahkonen%40maanmittauslaitos.fi%7C751680624f65498df41008db14ec07c5%7Cc4f8a63255804a1c92371d5a571b71fa%7C0%7C1%7C638126776216198394%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=nu1%2BBml9%2BZG%2BIvjJ8ZpRZ28kDVKzo960hSM%2F18s3Jng%3D&reserved=0> suggests it might no longer work for MapServer 8 (based on the heading "Using MapServer version < 8"), but the documentation at https://mapserver.org/pdf/MapServer.pdf<https://eur06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmapserver.org%2Fpdf%2FMapServer.pdf&data=05%7C01%7Cjukka.rahkonen%40maanmittauslaitos.fi%7C751680624f65498df41008db14ec07c5%7Cc4f8a63255804a1c92371d5a571b71fa%7C0%7C1%7C638126776216198394%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=OGoZ%2FK4IwX1%2FVRmcWsewiygoys24Vg4eDlGYIhtdcUk%3D&reserved=0> shows the same examples with the heading "Using MapServer version <= 8" on page 1065 of the PDF, so I'm unsure if this is still intended to work in MapServer 8.

Thank you,
Matt
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