import gdal
import cartopy

class EASE_North(cartopy.crs.Projection):
    
    def __init__(self):
        
        # see: http://www.spatialreference.org/ref/epsg/3408/
        proj4_params = {'proj': 'laea',
            'lat_0': 90.,
            'lon_0': 0,
            'x_0': 0,
            'y_0': 0,
            'a': 6371228,
            'b': 6371228,
            'units': 'm',
            'no_defs': ''}
        
        super(EASE_North, self).__init__(proj4_params)
        
    @property
    def boundary(self):
        coords = ((self.x_limits[0], self.y_limits[0]),(self.x_limits[1], self.y_limits[0]),
                  (self.x_limits[1], self.y_limits[1]),(self.x_limits[0], self.y_limits[1]),
                  (self.x_limits[0], self.y_limits[0]))
        
        return cartopy.crs.sgeom.Polygon(coords).exterior
        
    @property
    def threshold(self):
        return 1e5
    
    @property
    def x_limits(self):
        return (-9000000, 9000000)

    @property
    def y_limits(self):
        return (-9000000, 9000000)

# example data from:
# ftp://n4ftl01u.ecs.nasa.gov/SAN/OTHR/NISE.004/2013.09.30/

ds = gdal.Open('D:/NISE_SSMISF17_20130930.HDFEOS')

# this loads the layers for both hemispheres
data = np.array([gdal.Open(name, gdal.GA_ReadOnly).ReadAsArray()
                 for name, descr in ds.GetSubDatasets() if 'Extent' in name])

ds = None

# mask anything other then sea ice
sea_ice_concentration = np.ma.masked_where((data < 1) | (data > 100), data, 0)

lim = 3000000

fig, ax = plt.subplots(figsize=(8,8),subplot_kw={'projection': EASE_North(), 'xlim': [-lim,lim], 'ylim': [-lim,lim]})

land = cartopy.feature.NaturalEarthFeature(
            category='physical',
            name='land',
            scale='50m',
            facecolor='#dddddd',
            edgecolor='none')

#ax.add_feature(land)
ax.coastlines()

# from the metadata in the HDF
extent = [-9036842.762500, 9036842.762500, -9036842.762500, 9036842.762500]

ax.imshow(sea_ice_concentration[0,:,:], cmap=plt.cm.Blues, vmin=1,vmax=100,
          interpolation='none', origin='upper', extent=extent, transform=EASE_North())