Python如何使用osgeo.ogr.Geometry对象计算多边形周长

2019年8月4日 550次阅读

首先,我很抱歉发布这个简单的问题.我需要计算一定数量的宝石学属性(面积,周长,Roundess,长轴和短轴等).我使用
GDAL/OGR来读取多边形的shapefile格式.我想问的是：

>有没有使用osgeo.ogr.Geometry计算周长的方法？
>是否有用于计算多边形度量的模块构建？

提前致谢

    import osgeo.gdal, ogr
    poly="C:\\\myshape.shp"
    shp = osgeo.ogr.Open(poly)
    layer = shp.GetLayer()
    # For every polygon
    for index in xrange(len(allFID)):
        feature = layer.GetFeature(index)
        # get "FID" (Feature ID)
        FID = str(feature.GetFID())
        geometry = feature.GetGeometryRef()
        # get the area
        Area = geometry.GetArea()

最佳答案

        ref_geometry = ref_feature.GetGeometryRef()
        pts = ref_geometry.GetGeometryRef(0)
        points = []
        for p in xrange(pts.GetPointCount()):
            points.append((pts.GetX(p), pts.GetY(p)))

def edges_index(points):
    """
    compute edges index for a given 2D point set

    1- The number of edges which form the polygon
    2- Perimeter
    3- The length of the longest edge in a polygon
    4- The length of the shortest edge in a polygon
    5- The average length of all of edges in a polygon
    6- The lengths of edges deviate from their mean value
    """
    Nedges = len(points)-1
    length = []
    for i in xrange(Nedges):
        ax, ay = points[i]
        bx, by = points[i+1]
        length.append(math.hypot(bx-ax, by-ay))
    edges_perimeter = numpy.sum(length)
    edges_max = numpy.amax(length)
    edges_min = numpy.amin(length)
    edges_average = numpy.average(length)
    edges_std = numpy.std(length)
    return (Nedges,edges_perimeter,edges_max,edges_min,edges_average,edges_std)
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