Mapchete

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* ``vector.reproject_geometry()`` throws now ``shapely.errors.TopologicalError`` instead
of ``RuntimeError`` if reprojected geometry is invalid
* ``vector.reproject_geometry()`` now uses ``fiona.transform.transform_geom()`` internally
* pass on delimiters (zoom levels & process bounds) to drivers ``InputData`` object
* when a tile is specified in ``mapchete execute``, process bounds are clipped to tile
bounds
* better estimate ``chunksize`` for multiprocessing in tile processing & preparing inputs
* add nodata argument to ``read_raster_window()`` to fix ``rasterio.vrt.WarpedVRT``
resampling issue


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* better memory handling by detatching process output data from ``BufferedTile`` objects
* breaking API changes:

* ``Mapchete.execute()`` returns raw data instead of tile with data attribute
* ``Mapchete.read()`` returns raw data instead of tile with data attribute
* ``Mapchete.get_raw_output()`` returns raw data instead of tile with data attribute
* ``Mapchete.write()`` requires process_tile and data as arguments
* same valid for all other ``read()`` and ``write()`` functions in drivers &
``MapcheteProcess`` object
* formats ``is_empty()`` function makes just a basic intersection check but does not
actually look into the data anymore
* formats ``read()`` functions are not generators anymore but follow the rasterio style
(2D array when one band index is given, 3D arrays for multiple band indices)

* new ``MapcheteNodataTile`` exception to indicate an empty process output
* raster_file & geotiff Input cache removed
* ``get_segmentize_value()`` function is now public
* use ``rasterio.vrt.WarpedVRT`` class to read raster windows
* source rasters without nodata value or mask are now handled properly (previously a
default nodata value of 0 was assumed)


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* removed GDAL from dependencies by reimplementing ogr ``segmentize()`` using shapely
* use ``cascaded_union()`` instead of ``MultiPolygon`` to determine process area


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* process file now will accept a simple ``execute(mp)`` function
* current version number is now accessable at ``mapchete.__version`` (77)
* added ``--version`` flag to command line tools


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* fixed PNG alpha band handling
* added generic ``MapcheteEmptyInputTile`` exception
* internal: available pyramid types are now loaded dynamically from ``tilematrix``
* closed 25: use HTTP errors instead of generating pink tiles in ``mapchete serve``


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* ``input_files`` config option now raises a deprecation warning and will be replaced with
``input``
* abstract ``input`` types are now available which is necessary for additional non-file
based input drivers such as DB connections
* improved antimeridian handling in ``create_mosaic()`` (69)
* improved baselevel generation performance (74)


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