mapbox切片原理
参考： github.com/jingsam/vec…
示例：
线要素：
假设示例线要素的坐标为:
-
(2,2)
-
(2,10)
-
(10,10) 编码需要3条指令：
-
MoveTo(+2,+2)
-
LineTo(+0,+8)
-
LineTo(+8,+0)
使用postgis进行矢量瓦片切片
示例sql
select ST_AsMVT(P, 'adcode', 4096, 'geom') as "mvt" from ( select fid, ST_AsMVTGeom(ST_Transform(geom, 3857),ST_Transform(ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326), 3857), 4096, 64, TRUE) geom FROM adcode where ST_Transform(geom, 4326) && ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326) ) AS P;
sql详解
1. ST_AsMVTGeom
1.1 函数
geometry ST_AsMVTGeom(geometry geom, box2d bounds, integer extent=4096, integer buffer=256, boolean clip_geom=true);
1.2 描述
将一个图层中位于参数box2d范围内的一个几何图形的所有坐标转换为MapBox VectorTile坐标空间里的坐标。
函数各个参数的含义：
- geom —— 被转换的几何图形信息。
- bounds —— 某个矢量切片的范围对应的空间参考坐标系中的几何矩形框（没有缓冲区）。
- extent —— 是按规范定义的矢量切片坐标空间中的某个矢量切片的范围。如果为NULL，则默认为4096（边长为4096个单位的正方形）。
- buffer —— 矢量坐标空间中缓冲区的距离，位于该缓冲区的几何图形部位根据clip_geom参数被裁剪或保留。如果为NULL，则默认为256。
- clip_geom —— 用于选择位于缓冲区的几何图形部位是被裁剪还是原样保留。如果为NULL，则默认为true。
extent说明：
瓦片的extent只是指明了瓦片的范围，并不是瓦片的渲染之后的大小。例如一张extent为4096的矢量瓦片，并不意味着最终渲染出来的是一张4096 X 4096大小的图片。渲染出的图片大小并不由extent决定，通常会被渲染为256 X 256或512 X 512大小的图片。假设将一张extent为4096的矢量瓦片渲染为256 X 256大小的图片，那么(0, 0)~(16, 16)坐标范围内的点都将被综合到图片上的(0, 0)像素点。
2.ST_AsMVT
2.1 函数
bytea ST_AsMVT(anyelement row, text name, integer extent, text geom_name)
2.2 描述
ST_AsMVT聚合函数用于将基于MapBox VectorTile坐标空间的几何图形转换为MapBox VectorTile二进制矢量切片。
3.其余说明
3.1 adcode
adcode 为source_layer名称，用于前端锁定该图层的唯一值
3.2 where语句
where语句完成了求交操作，在转矢量瓦片之前，先对数据进行一遍筛选
一个服务包含多个图层
可以通过" || "操作符调用多次这个函数来同时创建多个图层的同一位置的矢量切片。
select (
(select ST_AsMVT(P, 'adcode', 4096, 'geom') as "mvt" from (
select fid, ST_AsMVTGeom(ST_Transform(geom, 3857),ST_Transform(ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326), 3857),
4096, 64, TRUE) geom FROM adcode
where ST_Transform(geom, 4326) && ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326)
) AS P)
||
(select ST_AsMVT(P, 'adcode_many', 4096, 'geom') as "mvt" from (
select fid, ST_AsMVTGeom(ST_Transform(geom, 3857),ST_Transform(ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326), 3857),
4096, 64, TRUE) geom FROM adcode_many
where ST_Transform(geom, 4326) && ST_MakeEnvelope(112.5,31.952162238024968,123.75,21.943045533438177, 4326)
) AS P)
) as mvt;
服务元信息提供格式
{
"vector_layers": [
{
"id": "adcode",
"description": "",
"minzoom": 3,
"maxzoom": 14,
"fields": {
"RuleID": "Number",
"Shape_Area": "Number",
"Shape_Le_1": "Number",
"市": "String",
"市代码": "Number",
"总就业": "Number",
"省": "String",
"省代码": "Number",
"第一产": "Number",
"第三产": "Number",
"第二产": "Number",
"类型": "String"
}
},
{
"id": "point",
"description": "",
"minzoom": 3,
"maxzoom": 14,
"fields": {
"code": "Number",
"fclass": "String",
"name": "String",
"osm_id": "String",
"population": "Number"
}
}
],
"tilestats": {
"layerCount": 2,
"layers": [
{
"layer": "adcode",
"count": 26,
"geometry": "Polygon",
"attributeCount": 12,
"attributes": [
{
"attribute": "RuleID",
"count": 1,
"type": "number",
"values": [
1
],
"min": 1,
"max": 1
},
{
"attribute": "Shape_Area",
"count": 26,
"type": "number",
"values": [
11012620975.4,
11058238780.5,
11258930970.1,
11924978433.2,
12623024234.6,
12705803151.2,
13279558658.7,
14393233922.6,
15852808860.2,
16703625432.3,
1774440792.53,
18283423503.5,
19077078711.9,
22344759914.4,
22494633204.7,
4085632634.67,
5360067329.32,
5625141484.19,
6046665522.68,
6385337094.48,
6665811495.99,
7899075155.52,
8174638447.95,
8222804709.16,
9171489130.24,
9335756097.46
],
"min": 1774440792.53,
"max": 22494633204.7
},
{
"attribute": "Shape_Le_1",
"count": 26,
"type": "number",
"values": [
1011873.27782,
1012186.08944,
1084830.48336,
1188628.83669,
1381168.14064,
1412294.26897,
1469324.21953,
458880.374513,
463538.154366,
525787.62611,
562273.302328,
616655.303771,
640510.689051,
651483.331289,
676977.345371,
682944.783658,
702248.058441,
707310.820758,
710747.278107,
728183.668113,
760630.773967,
784751.376285,
799571.995724,
845650.400553,
894482.8917,
913078.633567
],
"min": 458880.374513,
"max": 1469324.21953
},
{
"attribute": "市",
"count": 26,
"type": "string",
"values": [
"上海市",
"南京市",
"南通市",
"台州市",
"合肥市",
"嘉兴市",
"宁波市",
"安庆市",
"宣城市",
"常州市",
"扬州市",
"无锡市",
"杭州市",
"池州市",
"泰州市",
"湖州市",
"滁州市",
"盐城市",
"绍兴市",
"舟山市",
"芜湖市",
"苏州市",
"金华市",
"铜陵市",
"镇江市",
"马鞍山市"
]
},
{
"attribute": "市代码",
"count": 26,
"type": "number",
"values": [
310000,
320100,
320200,
320400,
320500,
320600,
320900,
321000,
321100,
321200,
330100,
330200,
330400,
330500,
330600,
330700,
330900,
331000,
340100,
340200,
340500,
340700,
340800,
341100,
341700,
341800
],
"min": 310000,
"max": 341800
},
{
"attribute": "总就业",
"count": 26,
"type": "number",
"values": [
114.6,
116.5,
1375.66,
144.3,
191.5,
194.8,
204,
221.8,
267.1,
275.5,
282.2,
310.4,
334.2,
335.5,
346,
353.5,
388.2,
407.79,
431.8,
455,
462.6,
542.8,
560,
692.3,
696.1,
75.1
],
"min": 75.1,
"max": 1375.66
},
{
"attribute": "省",
"count": 4,
"type": "string",
"values": [
"上海市",
"安徽省",
"江苏省",
"浙江省"
]
},
{
"attribute": "省代码",
"count": 4,
"type": "number",
"values": [
310000,
320000,
330000,
340000
],
"min": 310000,
"max": 340000
},
{
"attribute": "第一产",
"count": 26,
"type": "number",
"values": [
10.55,
105,
109.3,
15.61,
15.8,
21.09,
21.7,
21.9,
26.84,
29.4,
33.3,
33.6,
39.4,
40.83,
42.6,
42.7,
45.05,
49.3,
55.7,
59.7,
64.2,
67.84,
69.04,
70.4,
83.7,
95.9
],
"min": 10.55,
"max": 109.3
},
{
"attribute": "第三产",
"count": 26,
"type": "number",
"values": [
107.3,
107.9,
108.5,
108.9,
115.4,
118.4,
120.87,
127.04,
148.6,
156.3,
158.8,
159.7,
177.4,
254.05,
264.8,
273.8,
282.9,
35.36,
392.1,
43.9,
51.4,
68.1,
76.13,
82.4,
87.8,
912.01
],
"min": 35.36,
"max": 912.01
},
{
"attribute": "第二产",
"count": 26,
"type": "number",
"values": [
106.5,
111.9,
120.4,
137.4,
146.2,
158.5,
163.59,
174.51,
180.06,
183.7,
189.5,
211.6,
213.6,
244.3,
28,
29.19,
290.34,
31.8,
405.8,
42.6,
422.82,
57.4,
63.6,
85.1,
94.28,
96.9
],
"min": 28,
"max": 422.82
},
{
"attribute": "类型",
"count": 3,
"type": "string",
"values": [
"副省级市",
"地级市",
"直辖市"
]
}
]
},
{
"layer": "point",
"count": 16492,
"geometry": "Point",
"attributeCount": 5,
"attributes": [
{
"attribute": "code",
"count": 9,
"type": "number",
"values": [
1001,
1002,
1003,
1004,
1010,
1020,
1030,
1041,
1050
],
"min": 1001,
"max": 1050
},
{
"attribute": "fclass",
"count": 9,
"type": "string",
"values": [
"city",
"county",
"farm",
"hamlet",
"island",
"locality",
"suburb",
"town",
"village"
]
},
{
"attribute": "name",
"count": 1000,
"type": "string",
"values": [
",隔溪张村",
"Anjia",
"Aofan",
"Bai Sha Lin Chang",
"Beilu",
"Caizhai",
"Guishan",
"Haohantu",
"Huitouwan",
"Kengkou",
"Longgong",
"Ma'ao",
"Malingkou",
"Nanlinghu",
"Pancun",
"Shang'ao",
"Shimulong",
"Shuangjin",
"Tangjiawang",
"Tantou Island",
"Xia",
"Xiaohuangtang",
"Xiaojia",
"Xiheng",
"Yangjia",
"Yaohu",
"Yinkeng",
"Yu'ao",
"Zhaitou Jiao",
"Zhongduan",
"Zishazhou",
"e修鸽家电维修",
"xiaomaowu",
"㫃塘坞口",
"一一七社区",
"一市镇",
"一沟里",
"一社",
"一统碑",
"一都孙村",
"一都村",
"丁伙镇",
"丁兰社区",
"丁兰街道",
"丁北",
"丁卯街道",
"丁堰街道",
"丁堰镇",
"丁塘村",
"丁塘社区",
"丁宅乡",
"丁家",
"丁家村",
"丁家桥镇",
"丁家畈村",
"丁小郢",
"丁山河村",
"丁山社区",
"丁岗",
"丁岗镇",
"丁店",
"丁所",
"丁村",
"丁架形",
"丁桥苑社区",
"丁桥镇",
"丁棚",
"丁沟镇",
"丁河村",
"丁涧店",
"丁程",
"丁舍",
"丁蜀镇",
"丁西",
"丁郢",
"丁香镇",
"七井乡",
"七亩丘",
"七古登社区",
"七圩社区",
"七坞口",
"七坞岗",
"七堡社区",
"七大户",
"七家坞",
"七峰村",
"七广",
"七庄村",
"七房",
"七星街道",
"七星镇",
"七林湾村",
"七格社区",
"七洲",
"七甲闸社区",
"七联",
"七贤桥村",
"七都镇",
"七里",
"七里亭村"
]
},
{
"attribute": "osm_id",
"count": 1000,
"type": "string",
"values": [
"1036411320",
"1070286782",
"1338631346",
"1339088743",
"1439717507",
"1568725594",
"1568726755",
"1586567000",
"1588003393",
"1594147431",
"1594196001",
"1594197516",
"1594198529",
"1594199575",
"1594280307",
"1594726979",
"1594728656",
"1594730193",
"1594840800",
"1603607841",
"1603607844",
"1603607857",
"1611212497",
"1612053447",
"1618586303",
"1642883473",
"1666058767",
"1669502051",
"1675935512",
"1675935515",
"1699224580",
"1699224581",
"1699224582",
"1699224587",
"1699224591",
"1699224592",
"1699224593",
"1699224594",
"1699703343",
"1699703354",
"1699703360",
"1699703377",
"1699703383",
"1699703387",
"1699703400",
"1699703408",
"1699703421",
"1699703426",
"1699703429",
"1699703457",
"1699703465",
"1699703467",
"1699703489",
"1699703502",
"1699703507",
"1699703518",
"1699703527",
"1699703536",
"1699703553",
"1699703558",
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"1699703586",
"1699703596",
"1699703604",
"1699703612",
"1699703623",
"1699703647",
"1699703651",
"1699703657",
"1699703674",
"1699703678",
"1699703683",
"1699703707",
"1699703711",
"1699703727",
"1699703732",
"1699703736",
"1699703758",
"1699703765",
"1699703769",
"1699703784",
"1699703796",
"1699703806",
"1699703821",
"1699703829",
"1699703832",
"1699703851",
"1699703860",
"1699703873",
"1699703884",
"1699761800",
"1699761816",
"1699761826",
"1699761834",
"1699761838",
"1699761863",
"1699761874",
"1699761888",
"1699761940",
"1699761954"
]
},
{
"attribute": "population",
"count": 106,
"type": "number",
"values": [
0,
1000,
100000,
102000,
10465994,
109000,
110000,
1121261,
12000,
120000,
126000,
13000,
130000,
132000,
14000,
143149,
143600,
1500,
150000,
15550000,
160000,
1620000,
1700000,
181000,
184729,
20,
2000,
200000,
21000,
220000,
22728,
23000,
2304774,
24000,
2400000,
2500,
257764,
2600,
260000,
2601000,
2800,
28000,
2893542,
3000,
30000,
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4000,
40000,
400000,
41203,
41409,
4500,
45000,
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5000,
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8000,
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],
"min": 0,
"max": 15550000
}
]
}
]
}
}
