Pycoast supports plotting of polygons and polylines from ESRI shapefiles, currently only in lonlat coordinates format. In the following example we use :attr:`add_shapefile_shapes` method to plot all line shapes found in the file Metareas.shp. We then use the :attr:`add_shapefile_shape` (notice the singular) to plot only the 3rd and 4th shape_id within the file BR_Regioes.shp.
>>> from pycoast import ContourWriterAGG >>> img = Image.new('RGB', (600, 600)) >>> proj4_string = '+proj=merc +lon_0=-60 +lat_ts=-30.0 +a=6371228.0 +units=m' >>> area_extent = (-2000000.0, -5000000.0, 5000000.0, 2000000.0) >>> area_def = (proj4_string, area_extent) >>> cw = ContourWriterAGG(gshhs_root_dir) ... >>> cw.add_coastlines(img, area_def, resolution='l', level=4) >>> cw.add_shapefile_shapes(img, area_def, 'test/test_data/shapes/Metareas.shp', outline='red',width=2) >>> cw.add_shapefile_shape(img, area_def, 'test/test_data/shapes/divisao_politica/BR_Regioes.shp', 3, outline='blue') >>> cw.add_shapefile_shape(img, area_def, 'test/test_data/shapes/divisao_politica/BR_Regioes.shp', 4, outline='blue', fill='green')
If your shapefile is not in lonlat coordinates, then you can re-project your shape file using :attr:`ogr2ogr` (part of GDAL tools), e.g.
$ ogr2ogr original.shp lonlat.shp -t_srs "+proj=latlong"
This should work if you have all the extra meta-files original.* included with your original.shp. Please refer to the OGR documentation for more information.
To further customize how shapes are drawn the
:meth:`~pycoast.ContourWriterAGG.add_shapes` can be used. This is the low-level
version of the add_shapefile_shape
method described above. This method
takes an iterable of shape objects to draw with optional drawing parameters.
In combination with python generators this can provide a high performance
method for drawing multiple shapes with per-shape customization.
In the below example a custom generator function is defined to open a shapefile
and specify that each polygon should be blue and any other shape should be red.
>>> import shapefile >>> def my_shapes_generator(): ... sf = shapefile.Reader(filename) ... for shape in sf.shapes(): ... if shape.shapeType == shapefile.POLYGON: ... kwargs = {'fill': (0, 0, 255)} ... else: ... kwargs = {'fill': (255, 0, 0)} ... yield (shape, kwargs) ... cw.add_shapes(img, area_def, my_shapes_generator())