Question

从Python GDAL/OGR Cookbook 1.0 documentation开始，我在字符串格式中插入一个“in memory”geojson，在loop_zonal_stats中插入一个gdal“in memory”栅格作为input_zone_polygon，然后我从zonal_stats（）中为每个特征接收一个int值。该值由FID存储在字典中。

原始代码：

def loop_zonal_stats(input_zone_polygon, input_value_raster):

    shp = ogr.Open(input_zone_polygon)
    lyr = shp.GetLayer()
    featList = range(lyr.GetFeatureCount())
    statDict = {}

    for FID in featList:
        feat = lyr.GetFeature(FID)
        maxValue = zonal_stats(feat, input_zone_polygon, input_value_raster)
        statDict[FID] = int(maxValue)
    return statDict

print statDict 
{0: 5, 1: 5, 2: 5, 3: 5, ...}

目标是添加一个名为Densitykm2的字段，并使用从zonal_stats（）直接在geojson“in memory”中获取的值填充它。这个更新过的geojson将是该方法的返回。

所以这是修改后的代码：

def loop_zonal_stats(input_zone_polygon, input_value_raster):

    shp = ogr.Open(input_zone_polygon)
    lyr = shp.GetLayer()
    featList = range(lyr.GetFeatureCount())
    maxFldDef = ogr.FieldDefn('Densitykm2', ogr.OFTInteger)
    lyr.CreateField(maxFldDef)

    for FID in featList:
        feat = lyr.GetFeature(FID)
        maxValue = zonal_stats(feat, input_zone_polygon, input_value_raster)
        feat.SetField('Densitykm2', int(maxValue))
        lyr.SetFeature(feat)
    return input_zone_polygon

然而，我尝试过收到两种错误：

错误6：不支持内联定义更新
列表错误1：索引无效：-1

也许还有另一种可能性，将“内存中”geojson与原始代码的返回字典合并到Add字段并填充它。也许用geojson lib？

- 更新 -

这是一个解决方案，我代码：

def loop_zonal_stats(input_zone_polygon, input_value_raster):
    # Load Polygon
    shp = ogr.Open(input_zone_polygon)
    lyr = shp.GetLayer()
    # Density field Definition
    maxFldDef = ogr.FieldDefn('Densitykm2', ogr.OFTInteger)
    # Create Temporary memory layer
    outdriver = ogr.GetDriverByName('MEMORY')
    source = outdriver.CreateDataSource('memData')
    outdriver = outdriver.Open('MEM', 1)
    # Copy of Polygon layer
    source.CopyLayer(lyr, 'temp', ['OVERWRITE=YES'])
    # Load temp Temporary memory layer
    memlyr = source.GetLayer()
    # Density Field creation
    memlyr.CreateField(maxFldDef)
    # List of ID to enumerate on
    featList = range(lyr.GetFeatureCount())
    print "Number of Wetlands in process  = {0}".format(len(featList))
    # input SpatialReference
    inSpatialRef = osr.SpatialReference()
    inSpatialRef.ImportFromEPSG(2959)
    # input SpatialReference
    outSpatialRef = osr.SpatialReference()
    outSpatialRef.ImportFromEPSG(4326)
    # create the CoordinateTransformation
    coordTrans = osr.CoordinateTransformation(inSpatialRef, outSpatialRef)
    # Empty list to be filled with Geojon Feature Objet = []
    GeojonFeatObj = []
    # Loop over features
    for FID in featList:
        FeatIn = lyr.GetFeature(FID)
        # Get feature of Polygon
        featOut = memlyr.GetFeature(FID)
        # get ZonalStats
        maxValue = zonal_stats(FeatIn, input_zone_polygon, input_value_raster)
        # Add density to feature
        featOut.SetField('Densitykm2', maxValue)
        print "Wetlands features proceed FID = {0} / {1}".format(FID, len(featList))
        # write the feature to the layer
        memlyr.SetFeature(featOut)
        # Get geometry
        geom = featOut.GetGeometryRef()
        # Transform geometry (UTM18N ---> WGS84)
        geom.Transform(coordTrans)
        # update feature geometry
        featOut.SetGeometry(geom)
        # Export the feature to a feature geojson
        GeojonFeatObj.append(featOut.ExportToJson())

    return GeojonFeatObj

请注意，您需要： - 为要素对象列表构建FeatureCollection - 添加crs作为前缀 - 清理ORG字符串混乱

fc = geojson.FeatureCollection(tupple)
    outputGeojson = geojson.dumps(fc)
    #outputGeojson.replace(,'') }, {"geometry":
    prefix = '{"crs": {"type": "link", "properties": {"href": "http://spatialreference.org/ref/epsg/4326/", "type": "proj4"}}, '
    output = prefix+outputGeojson[1:]
    output = output.replace('\\', '').replace('}"]', '}]').replace('["{', '[{').replace('", "{"geometry":', ', {"geometry":')

亚历

将字段添加到geojson并填充它 - python

0 个答案: