This allows for custom raster styles to be defined with base: raster. The raster style is derived from the polygons rendering style, and provides the same shader blocks. max-display-density allows a cap to be set on oversampling, to limit texture memory use.

alpha sets an alpha value for the entire data source.composite allows multiple images to be combined into a single data source.Three additional parameters exist for fine-tuning raster behavior: This example shows a USGS historical map from the Chelan, WA area, overlaid on top of the Mapzen Walkabout base map:

Url: images/chelan.jpg # no tile XYZ pattern in URL indicates standalone imageīounds: # geo-extent of the image Type: Raster # can now indicate either tiled or un-tiled image source Untiled raster image data may also be loaded, by specifying a single image file in the source's url parameter, as well as a bounding box in the bounds parameter: sources: This gif compares Mapzen terrain normal tiles to a version using zoom_offset: 1, effectively generalizing the terrain while lowering network bandwidth: ( zoom_offset also works for vector data!) The zoom_offset parameter allows the user to request lower zooms for each zoom level, reducing tile size and visual detail. In some circumstances, the default tiles for a source may be either too large (in file size) or too detailed (in feature density or coordinate precision) than needed for the current application. The default value for url_density_scales is, meaning it will load either 'plain' tile URLs like tile.png, or tiles on displays with a display density >= 2. For example, Wikimedia maps has several resolutions, which can be rendered in Tangram with: sources: Multiple resolutions can be supported with the url_density_scales parameter. However, other resolutions are also possible. The most common case is a source that supports 1x and 2x tiles, and this is the default configuration. A source url which includes the URL template token, as shown below: This is done by specifying a source of type raster, either tiled or untiled. The simplest way to use raster data is to display it directly, without any combinations or modifications. Tangram allows raster data sources to be loaded, displayed, and combined with vector data sources in a variety of ways, including with real-time image manipulation.

Example of raster image