The Background requirements class describes how to define the background of the map that is presented.
The Maps API core requirements class defines how to get a map. The Map operation requirements class specifies parameters supporting customization of the background of the map.
The transparent and bgcolor parameters indicate how the absence of data will be represented in the map, what color will show underneath any non-opaque layer, and allow for the map to be overlaid with other maps without completely obscuring the lower layers.
The list of W3C web color names which can be specified instead of a hexadecimal value can be found in [annex_bgcolor]
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When not specified, the value of transparent defaults to true when bgcolor is not used, but to false when used together with bgcolor.
For formats with an alpha channel, explicitly setting transparent=true together with a bgcolor allows for defining the color value to use for the RGB channels where there is no data. Zero (0) will be used for the alpha channel.
For formats reserving a color to define transparency (color key), the combination supports selecting a color that does not interfere with the actual values and colors in the map.
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The opaque attribute of layer element in the GetCapabilities response in WMS is not specified by the Maps API.
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The void-transparent and void-color parameters indicate how parts of the map outside of the valid area of the projection and CRS will be represented.
If not specified, these parameters default to the same value as transparent and bgcolor, respectively.
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These parameters only apply to CRSs including an invalid area, such as a CRS using an orthographic projection. |
As for bgcolor, the W3C web color names can be specified instead of a hexadecimal value.
A successful GET response is described in the core class (https://www.opengis.net/spec/ogcapi-maps-1/1.0/conf/core)