55 lines
2.9 KiB
Plaintext
55 lines
2.9 KiB
Plaintext
/**
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* The ol.proj namespace stores:
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* * a list of {@link ol.proj.Projection}
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* objects, one for each projection supported by the application
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* * a list of transform functions needed to convert coordinates in one projection
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* into another.
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*
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* The static functions are the methods used to maintain these.
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* Each transform function can handle not only simple coordinate pairs, but also
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* large arrays of coordinates such as vector geometries.
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*
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* When loaded, the library adds projection objects for EPSG:4326 (WGS84
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* geographic coordinates) and EPSG:3857 (Web or Spherical Mercator, as used
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* for example by Bing Maps or OpenStreetMap), together with the relevant
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* transform functions.
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*
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* Additional transforms may be added by using the {@link http://proj4js.org/}
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* library (version 2.2 or later). You can use the full build supplied by
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* Proj4js, or create a custom build to support those projections you need; see
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* the Proj4js website for how to do this. You also need the Proj4js definitions
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* for the required projections. These definitions can be obtained from
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* {@link http://epsg.io/}, and are a JS function, so can be loaded in a script
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* tag (as in the examples) or pasted into your application.
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* The first time there is a request for a projection, either with a
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* {@link ol.proj.projectionLike} or directly with {@link ol.proj.get}, the
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* code will check if the Proj4js library and the necessary definition are
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* loaded; if so, it will register the appropriate {@link ol.proj.Projection}
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* object and add transform functions between the new projection and all the
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* existing ones. See examples/wms-image-custom-proj for an example of this.
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* Because the check for presence of the Proj4js library and the definition only
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* takes place on the first request for them, this means they can be loaded
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* dynamically as needed; for example, with user-supplied data where you don't
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* know in advance what projections are needed, you can initially load minimal
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* support and then load whichever are requested.
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*
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* Note that Proj4js does not support projection extents. If you want to add
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* one for creating default tile grids, you can add it after the Projection
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* object has been created with `setExtent`, for example,
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* `ol.proj.get('EPSG:1234').setExtent(extent)`.
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*
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* In addition to Proj4js support, any transform functions can be added with
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* {@link ol.proj.addCoordinateTransforms}. To use this, you must first create
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* a {@link ol.proj.Projection} object for the new projection and add it with
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* {@link ol.proj.addProjection}. You can then add the forward and inverse
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* functions with {@link ol.proj.addCoordinateTransforms}. See
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* examples/wms-custom-proj for an example of this.
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*
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* Note that if no transforms are needed and you only need to define the
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* projection, just add a {@link ol.proj.Projection} with
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* {@link ol.proj.addProjection}. See examples/wms-no-proj for an example of
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* this.
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*
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* @namespace ol.proj
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*/
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