1Vector Features 2=============== 3 4Rasterio's ``features`` module provides functions to extract shapes of raster 5features and to create new features by "burning" shapes into rasters: 6``shapes()`` and ``rasterize()``. These functions expose GDAL functions in 7a general way, using iterators over GeoJSON-like Python objects instead of 8GIS layers. 9 10Extracting shapes of raster features 11------------------------------------ 12 13Consider the Python logo. 14 15.. image:: https://farm8.staticflickr.com/7018/13547682814_f2e459f7a5_o_d.png 16 17The shapes of the foreground features can be extracted like this: 18 19.. code-block:: python 20 21 import pprint 22 import rasterio 23 from rasterio import features 24 25 with rasterio.open('13547682814_f2e459f7a5_o_d.png') as src: 26 blue = src.read(3) 27 28 mask = blue != 255 29 shapes = features.shapes(blue, mask=mask) 30 pprint.pprint(next(shapes)) 31 32 # Output 33 # pprint.pprint(next(shapes)) 34 # ({'coordinates': [[(71.0, 6.0), 35 # (71.0, 7.0), 36 # (72.0, 7.0), 37 # (72.0, 6.0), 38 # (71.0, 6.0)]], 39 # 'type': 'Polygon'}, 40 # 253) 41 42The shapes iterator yields ``geometry, value`` pairs. The second item is the 43value of the raster feature corresponding to the shape and the first is its 44geometry. The coordinates of the geometries in this case are in pixel units 45with origin at the upper left of the image. If the source dataset was 46georeferenced, you would get similarly georeferenced geometries like this: 47 48.. code-block:: python 49 50 shapes = features.shapes(blue, mask=mask, transform=src.transform) 51 52Burning shapes into a raster 53---------------------------- 54 55To go the other direction, use ``rasterize()`` to burn values into the pixels 56intersecting with geometries. 57 58.. code-block:: python 59 60 image = features.rasterize( 61 ((g, 255) for g, v in shapes), 62 out_shape=src.shape) 63 64By default, only pixels whose center is within the polygon or that 65are selected by Bresenham's line algorithm will be burned in. 66You can specify ``all_touched=True`` to burn in all pixels touched by the geometry. 67The geometries will be rasterized by the "painter's algorithm" - 68geometries are handled in order and later geometries will overwrite earlier values. 69 70Again, to burn in georeferenced shapes, pass an appropriate transform for the 71image to be created. 72 73.. code-block:: python 74 75 image = features.rasterize( 76 ((g, 255) for g, v in shapes), 77 out_shape=src.shape, 78 transform=src.transform) 79 80The values for the input shapes are replaced with ``255`` in a generator 81expression. Areas not covered by input geometries are replaced with an 82optional ``fill`` value, which defaults to ``0``. The resulting image, 83written to disk like this, 84 85.. code-block:: python 86 87 with rasterio.open( 88 '/tmp/rasterized-results.tif', 'w', 89 driver='GTiff', 90 dtype=rasterio.uint8, 91 count=1, 92 width=src.width, 93 height=src.height) as dst: 94 dst.write(image, indexes=1) 95 96has a black background and white foreground features. 97 98.. image:: https://farm4.staticflickr.com/3728/13547425455_79bdb5eaeb_o_d.png 99 100