The Web AppBuilder Geoprocessing widget output does not recognize transparencies in layer files used in the script tool and ModelBuilder output symbology properties.
Last Published: February 5, 2016ArcGIS Online
Bug ID Number
November 16, 2015
September 22, 2022
Will Not Be Addressed
The development team has considered the issue or request and concluded it will not be addressed. The issue's Additional Information section may contain further explanation.
The issue mentioned that the buffer result had symbology from a .lyr file which contains transparency, but client side does not respect the transparency. It is normal, not a bug.
If a result map service is used to draw geoprocessing output, what the client side does is adding a related dynamic layer. The source of this dynamic layer is a MapServer (http://csc-bwatson7d.esri.com/arcgis/rest/services/PointBufferOutputSymbology/MapServer for the sample above). The MapServer itself does not contain transparency value, what the client side get is actually an image.
At what place does the transparency take effect? It is not obvious if the user have only one layer in the result map service. If the user have two layers in the result map service, the transparency of the first layer is 50%. This time the user gets an image at client side which is fused by two layers and they are all visible, the first layer is 50% transparency. Things become more interesting when there are multiple layers in a MapServer and each of them has different transparency.
To set transparency for the result map service layer, do it in Layerlist widget. On the premise that the image format type supports transparency, such as PNG.