maskout.py

#coding=utf-8
###################################################################################################################################
#####This module enables you to maskout the unneccessary data outside the interest region on a matplotlib-plotted output instance
####################in an effecient way,You can use this script for free     ########################################################
#####################################################################################################################################
#####USAGE: INPUT  include           'originfig':the matplotlib instance##
#                                    'ax': the Axes instance
#                                    'shapefile': the shape file used for generating a basemap A
#                                    'region':the name of a region of on the basemap A,outside the region the data is to be maskout
#           OUTPUT    is             'clip' :the the masked-out or clipped matplotlib instance.
import shapefile
from matplotlib.path import Path
from matplotlib.patches import PathPatch
def shp2clip(originfig,ax,shpfile,region):
    sf = shapefile.Reader(shpfile)
    for shape_rec in sf.shapeRecords():
        if shape_rec.record[3] == region:  ####这里需要找到和region匹配的唯一标识符，record[]中必有一项是对应的。
            vertices = []
            codes = []
            pts = shape_rec.shape.points
            prt = list(shape_rec.shape.parts) + [len(pts)]
            for i in range(len(prt) - 1):
                for j in range(prt[i], prt[i+1]):
                    vertices.append((pts[j][0], pts[j][1]))
                codes += [Path.MOVETO]
                codes += [Path.LINETO] * (prt[i+1] - prt[i] -2)
                codes += [Path.CLOSEPOLY]
            clip = Path(vertices, codes)
            clip = PathPatch(clip, transform=ax.transData)
    for contour in originfig.collections:
        contour.set_clip_path(clip)
    return clip