Use Transparency Settings from a Map Service in a Web App

[SpencerV]

Hi, I am currently working on getting a map service I have published to display in a web app using the js API. I currently have 24 layers within the service, 4 of which are polygons that I want to have a slight transparency. I have set the transparency for those layers in the .mxd and was wondering how to carry that over to my web app.

When I load the service as a DynamicMapServiceLayer I am able to display my data but the transparency does not work. I can see a transparency value when I look at the individual layers in the service directory. I also noticed that if I pull my service into an arcgis.com map that the transparency is applied correctly for my 4 polygon layers. My service was published using desktop 10.2 to a 10.2 server instance.

I have done quite a bit of digging and have not been able to find an answer.  Based on the nature of the app I'd rather not break the service into multiple smaller services. Essentially I am looking for a way to use the transparency setting that is visible in the service in order to have transparency on individual layers.

Sorry if this has been asked before. I have not been able to find an answer that worked for me.

Thanks!

[TimWitt]

Spencer,

when you add the layer to your map you can always specify its transparency, via code, in its properties. See here.

Hope this helps!

Tim

[SpencerV]

Hi Tim,

Thanks for the response. Setting the opacity on the dynamic layer its self would make all the layers in the service transparent, correct? If so, I would like to only have the 4 polygon layers to be transparent while the remaining point layers are completely visible.

Thanks,
Spencer

[JakeSkinner]

Hi Spencer,

You could use the setVisibleLayers method to query which layers to add.  You could apply transparency to the polygons, and display the other layers with no transparency.  Ex:

//transparency applied
var lyrUSA = new ArcGISDynamicMapServiceLayer("http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer", {
      opacity : 0.5
});

lyrUSA.setVisibleLayers([0,2]);    
map.addLayer(lyrUSA);

//no transparency
var lyrUSA2 = new ArcGISDynamicMapServiceLayer("http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer");

lyrUSA2.setVisibleLayers([1,3]);
map.addLayer(lyrUSA2);

[SpencerV]

Hi Jake,

There is no way to utilize that transparency setting like the arcgis.com map does? Thanks for the response, looks like I will utilize the way you spoke of.

Thanks,
Spencer

[BrandonFlessner]

To set transparency for an individual layer, I had to enable support for dynamic layer on the map service in ArcGIS Server, set the image format to PNG32 for the dynamic layer --> layer.setImageFormat('png32'); There should be an easier way...

The problem with Jake Skinner's​ answer is that it will cause 2 requests to the map service every time the user pans, zooms, etc. If you have 24 layers with 24 different transparencies, this can quickly overwhelm a service.