Question

如何获取特定属性的多边形坐标。它是一个非常庞大的文件，所以解析文件的时间是一个因素。

有没有图书馆可以做到这一点？

geojson的样本：

{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:EPSG::37001" } },

"features": [
{ "type": "Feature", "properties": { "HOOD_ID": 2799.000000, "HOOD_NAME": "Overtown", "MARKET_ID": "MK1245000", "MARKET": "Miami", "STATE": "12", "STATENAME": "Florida", "LATITUDE": 25.784659, "LONGITUDE": -80.202625, "AREA": 1.495920, "HLEVEL": 2.000000, "DATE_ADDED": "2012\/08\/04", "FLAG1": 0, "OB_GEO_ID": "NH2799" }, "geometry": { "type": "Polygon", "coordinates": [ [ [ -80.21463341110001, 25.782154451300002 ], [ -80.21588353300001, 25.782696872700001 ], [ -80.217973576800006, 25.7833078056 ], [ -80.219539583200003, 25.784199528800002 ], [ -80.211531118000011, 25.787386122500003 ], [ -80.20836940560001, 25.789128957700001 ], [ -80.206422272200001, 25.789848709300003 ], [ -80.2060101207, 25.7907922853 ], [ -80.206013661300005, 25.793566844899999 ], [ -80.206013794, 25.7968569831 ], [ -80.202368489099996, 25.796952708299997 ], [ -80.202379, 25.797313 ], [ -80.199836, 25.797309 ], [ -80.199819759600004, 25.7970196375 ], [ -80.1993398571, 25.797032239699998 ], [ -80.193583490500004, 25.797234161599999 ], [ -80.193806159800005, 25.796203267299997 ], [ -80.194272724399994, 25.7951752727 ], [ -80.193944, 25.795182 ], [ -80.194266, 25.793434 ], [ -80.195336, 25.789592 ], [ -80.195534, 25.787847 ], [ -80.195514, 25.778409 ], [ -80.195969425200005, 25.778397321299998 ], [ -80.19557104899999, 25.773179598799999 ], [ -80.195360063199999, 25.768486166300001 ], [ -80.196768768399991, 25.7682545324 ], [ -80.198226099099998, 25.768721241800002 ], [ -80.199164023899996, 25.769800189500003 ], [ -80.199997701599997, 25.770738292499999 ], [ -80.200414826200003, 25.772286616100001 ], [ -80.200936435800003, 25.773272690900001 ], [ -80.202343232900006, 25.7749143389 ], [ -80.204375245, 25.776884093299998 ], [ -80.205990323199998, 25.777259031 ], [ -80.206835373600001, 25.777897973199998 ], [ -80.207587, 25.777601 ], [ -80.210881, 25.78 ], [ -80.21463341110001, 25.782154451300002 ] ] ] } },
{ "type": "Feature", "properties": { "HOOD_ID": 2169.000000, "HOOD_NAME": "Church District", "MARKET_ID": "MK1235000", "MARKET": "Jacksonville", "STATE": "12", "STATENAME": "Florida", "LATITUDE": 30.332174, "LONGITUDE": -81.660212, "AREA": 0.131745, "HLEVEL": 1.000000, "DATE_ADDED": "2012\/08\/04", "FLAG1": 0, "OB_GEO_ID": "NH2169" }, "geometry": { "type": "Polygon", "coordinates": [ [ [ -81.664799, 30.331204 ], [ -81.663868, 30.334826 ], [ -81.655617, 30.333239 ], [ -81.656717, 30.329439 ], [ -81.664799, 30.331204 ] ] ] } }
}

Answer 1

最好使用an event-based JSON parser解析大文件（这里我使用one by kuma-giyomu）。我们的想法是在遇到某个令牌时使用回调，这样就可以在解析之间完成数据的处理。

在下面的代码中，属性"coordinates"用于触发创建新的多边形对象，然后使用数组处理程序的start函数来启动新的坐标数组，并将其提交给多边形对象何时遇到数组结束标记。

<?php
include "JSONParser.php";

class Polygon {
    public $coordinates = array();
}
$coords = null;
$polygons = array();
$polygon = null;
$j = new JSONParser();
$j->setPropertyHandler(function($value, $property) {
    global $polygons, $polygon;
    if ($value != "coordinates") {
        if (!is_null($polygon)) {
            $polygons[] = $polygon;
            $polygon = null;
        }
        return;
    }

    if (is_null($polygon)) {
        $polygon = new Polygon;
    }
});
$j->setArrayHandlers(function($value, $property) {
    global $coords, $polygon;
    if (!is_null($polygon)) {
        $coords = array();
    }
}, function($value, $property) {
    global $coords, $polygon;
    if (!is_null($coords))  {
        if (!is_null($polygon)) {
            $polygon->coordinates[] = $coords;
        }
        $coords = null;
    }
});
$j->setScalarHandler(function($value, $property) {
    global $coords;
    if (!is_null($coords)) {
        $coords[] = $value;
    }
});

try {
    $j->parseDocument("test.json");
} catch (JSONParserException $e) {
}
if (!is_null($polygon)) {
    $polygons[] = $polygon;
    $polygon = null;
}

print_r($polygons);

输出

Array
(
[0] => Polygon Object
    (
        [coordinates] => Array
            (
                [0] => Array
                    (
                        [0] => -80.21463341110001
                        [1] => 25.782154451300002
                    )

                [1] => Array
                    (
                        [0] => -80.21588353300001
                        [1] => 25.782696872700001
                    )
                [...]

解析巨大的GeoJSON文件并获取特定属性的多边形坐标

1 个答案: