Overlay Layer Statement |  |
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Overlay Layer Statement| Syntax | OVERLAY LAYER '['PRELABELLING']', SOURCE <sourcelayer>, TARGET <targetlayer>, ALPHA <alphavalue> |
| Example | OVERLAY LAYER [PRELABELLING], SOURCE 1, TARGET 0, ALPHA 150 |
The Overlay Layer statement can be used to composite together streets rendered to auxiliary layers, with optional alpha transparency. Overlay Layer statements can only appear at the end of a map block, after all render blocks have been closed. This statement executes in the PreLabelling pass, so it will not affect any labels or shields drawn to auxiliary layers, as these are rendered in the Labelling pass.
Calling Overlay Layer clears the source layer, meaning it is no longer available for selective rendering when using the GeoBase JavaScript API, unless labels or shields have subsequently been rendered to that layer.
Parameterssourcelayer
The auxiliary layer to be composited onto the target layer. Integer value between 0 and 255 (inclusive). This layer should have been pre-populated through the use of the Aux Layer statement. This operation will result in the clearing of all content rendered on this layer.
targetlayer
The auxiliary layer onto which the source layer will be composited. Integer value between 0 and 255 (inclusive). If this layer did not previously exist, it will be created by this operation.
alphavalue
The alpha value to use when compositing the source layer onto the target. Integer value between 0 and 255 (inclusive) where 0 is fully transparent and 255 is fully opaque.