pgrouting_distance_isobands.py 文件源码

def __init__(self, params, zField='z'):
        ds = ogr.Open(connString)
        layer = ds.ExecuteSQL(OGR_SQL.format(*params))
        extent = layer.GetExtent()


        self.proj = layer.GetSpatialRef()
        self.geotransform = []        
        self.x = []
        self.y = []
        self.vals = []

        xMin, xMax, yMin, yMax = extent
        xSize, ySize = abs(xMax - xMin) / 0.0003, abs(yMin - yMax) / 0.0003
        self.size = xSize, ySize

        self.geotransform = [xMin, (xMax - xMin) / xSize, 0,
                             yMax, 0, (yMin - yMax) / ySize]


        feature = layer.GetNextFeature()        
        if feature.GetFieldIndex(zField) == -1:
            raise Exception('zField is not valid: ' + zField)
        while feature:  
            geometry = feature.GetGeometryRef()
            self.x.append(geometry.GetX())
            self.y.append(geometry.GetY()) 
            self.vals.append(feature.GetField(zField))  
            feature = layer.GetNextFeature()
        ds.Destroy()