1Masking a raster using a shapefile
2==================================
3Using ``rasterio`` with ``fiona``, it is simple to open a shapefile, read geometries, and mask out regions of a raster that are outside the polygons defined in the shapefile.
4
5.. code-block:: python
6
7        import fiona
8        import rasterio
9        import rasterio.mask
10
11        with fiona.open("tests/data/box.shp", "r") as shapefile:
12            shapes = [feature["geometry"] for feature in shapefile]
13
14This shapefile contains a single polygon, a box near the center of the raster, so in this case, our list of features is one element long.
15
16.. code-block:: python
17
18        with rasterio.open("tests/data/RGB.byte.tif") as src:
19            out_image, out_transform = rasterio.mask.mask(src, shapes, crop=True)
20            out_meta = src.meta
21
22Using ``plot`` and ``imshow`` from ``matplotlib``, we can see the region defined by the shapefile in red overlaid on the original raster.
23
24.. image:: ../img/box_rgb.png
25
26Applying the features in the shapefile as a mask on the raster sets all pixels outside of the features to be zero. Since ``crop=True`` in this example, the extent of the raster is also set to be the extent of the features in the shapefile. We can then use the updated spatial transform and raster height and width to write the masked raster to a new file.
27
28.. code-block:: python
29
30        out_meta.update({"driver": "GTiff",
31                         "height": out_image.shape[1],
32                         "width": out_image.shape[2],
33                         "transform": out_transform})
34
35        with rasterio.open("RGB.byte.masked.tif", "w", **out_meta) as dest:
36            dest.write(out_image)
37
38.. image:: ../img/box_masked_rgb.png
39