概述
很多地图可视化的项目中有要求实现如下的效果，本文借助QGIS、PS和turf.js，在mapboxGL中实现山体背景＋边界阴影的效果。
实现效果
image.png
实现
1. 需要数据
要实现这样的效果，我们需要如下数据：
- 山体背景图
- 地级市数据
- 省级边界数据，可通过地级市数据融合得到
- 边界阴影，通过省级边界数据计算获取
测试数据下载地址：https://gitee.com/lzugis15/blogs-demo/blob/master/gansu.zip
2. 数据处理
2.1 省级边界数据
如果没有改数据，可复制一份地级市的数据，在QGIS中开启图层编辑，全选要素，通过Merge选中要素生成。
image.png
2.2 山体背景图
1）导出影像
在QGIS中添加高德影像图，并添加省边界数据，设置省边界不显示，导出地图。
[图片上传中...(image.png-6c9beb-1716705916905-0)]
根据省边界数据计算导出范围，并设置导出格式为*.tif。
image.png
2）裁剪影像
将导出的*.tif添加到QGIS中，在Raster菜单下选择栅格裁剪工具，将导出的数据根据省边界数据进行裁剪。
image.png
3）导出背景图
跟操作1）一样，导出裁剪后的地图，导出格式选择*.png，导出后的图片如下图。
image.png
4）处理背景图
导出后的背景图是彩色的，还需要在PS中进一步处理成为蓝色调（可根据需求进行处理）。处理方式是在上面叠加一个图层，设置填充颜色，并设置模式为色相，再将两个图层合并成一个图层，处理后如下图。
image.png
2.3 边界阴影
边界阴影效果是将生边界数据进行一定的偏移，这个实现是在代码中实现的，实现代码如下：
const center = this.map.getCenter().toArray();
// 获取地图中心点屏幕位置
const { x, y } = this.map.project(center);
const offset = [6, 6];
// 计算当前级别下横向、纵向偏移的经纬度
const centerOffset = this.map.unproject([x - offset[0], y - offset[1]]).toArray();
const xOffset = centerOffset[0] - center[0],
yOffset = center[1] - centerOffset[1];
// 深拷贝，防止数据被篡改
const _res = JSON.parse(JSON.stringify(result));
const geometry = _res.geometry;
if (geometry.type === "polygon") {
geometry.coordinates.forEach((c) => {
c.forEach((p) => {
p[0] += xOffset;
p[1] += yOffset;
});
});
} else {
geometry.coordinates.forEach((c) => {
c.forEach((p) => {
p.forEach((_p) => {
_p[0] += xOffset;
_p[1] += yOffset;
});
});
});
}
3. 完整实现
完整实现代码如下。
<template>
<div class="map">
<my-map
:onLoad="mapLoaded"
:style="style"
:center="[104.29901000000001, 37.94116735562514]"
:zoom="zoom"
>
</my-map>
</div>
</template>
<script>
import { MyMap } from "@/components/map/index.vue";
import * as turf from "@turf/turf";
class Geojson {
constructor(features = []) {
this.features = features;
this.type = "FeatureCollection";
}
}
export default {
components: {
MyMap,
},
data() {
return {
map: null,
zoom: 3.51,
style: {
version: 8,
name: "my-map-style",
sprite: window.location.href + "icons/sprite",
glyphs: window.location.href + "fonts/{fontstack}/{range}.pbf",
sources: {
"image-admin": {
url: "/imgs/gansu-bg.png",
type: "image",
// 省边界数据的四至
coordinates: [
[92.3390100000000018, 42.795259999999999],
[108.712530000000001, 42.795259999999999],
[108.712530000000001, 32.5938900000000018],
[92.3390100000000018, 32.5938900000000018],
],
},
"admin-boundry": {
type: "geojson",
data: new Geojson(),
},
"admin-shadow": {
type: "geojson",
data: new Geojson(),
},
"admin-children-boundry": {
type: "geojson",
data: new Geojson(),
},
"admin-children-boundry-h": {
type: "geojson",
data: new Geojson(),
},
},
layers: [
{
id: "admin-shadow-fill",
source: "admin-shadow",
type: "fill",
paint: {
"fill-color": "#356caa",
"fill-opacity": 1,
},
},
{
id: "image-admin",
source: "image-admin",
type: "raster",
paint: {
"raster-opacity": 0.55,
"raster-fade-duration": 0,
},
},
{
id: "admin-children-boundry-fill",
source: "admin-children-boundry",
type: "fill",
paint: {
"fill-color": "#599AFF",
"fill-opacity": 0.1,
},
},
{
id: "admin-children-boundry-fill-h",
source: "admin-children-boundry-h",
type: "fill",
paint: {
"fill-color": "#599AFF",
"fill-opacity": 0.5,
},
},
{
id: "admin-children-boundry-line",
source: "admin-children-boundry",
type: "line",
paint: {
"line-color": "#bbe6ff",
"line-width": 1.5,
},
},
{
id: "admin-children-boundry-line-h",
source: "admin-children-boundry-h",
type: "line",
paint: {
"line-color": "#bbe6ff",
"line-width": 2,
},
},
{
id: "admin-boundry-line",
source: "admin-boundry",
type: "line",
paint: {
"line-color": "#bbe8ff",
"line-width": 3,
},
},
{
id: "admin-children-boundry-label",
source: "admin-children-boundry",
type: "symbol",
layout: {
'text-allow-overlap': false,
'text-size': 14,
'text-rotate': 0,
'text-field': `{name}`,
},
paint: {
'text-opacity': 1,
'text-color': '#ffffff',
'text-halo-blur': 0.1,
'text-halo-width': 0.1,
'text-halo-color': '#356caa',
},
},
],
},
adminFeatures: [],
};
},
methods: {
setBoundry(features) {
features = JSON.parse(JSON.stringify(features));
let result = features.splice(0, 1)[0],
feat2 = features.splice(0, 1)[0];
while (features.length > 0) {
result = turf.union(result, feat2);
feat2 = features.splice(0, 1)[0];
}
this.map.getSource("admin-boundry").setData(result);
setTimeout(() => {
const center = this.map.getCenter().toArray();
const { x, y } = this.map.project(center);
const offset = [6, 6];
const centerOffset = this.map
.unproject([x - offset[0], y - offset[1]])
.toArray();
const xOffset = centerOffset[0] - center[0],
yOffset = center[1] - centerOffset[1];
const _res = JSON.parse(JSON.stringify(result));
const geometry = _res.geometry;
if (geometry.type === "polygon") {
geometry.coordinates.forEach((c) => {
c.forEach((p) => {
p[0] += xOffset;
p[1] += yOffset;
});
});
} else {
geometry.coordinates.forEach((c) => {
c.forEach((p) => {
p.forEach((_p) => {
_p[0] += xOffset;
_p[1] += yOffset;
});
});
});
}
this.map.getSource("admin-shadow").setData(_res);
}, 200);
},
registerEvent() {
this.map.on("mousemove", "admin-children-boundry-fill", (e) => {
const adcode = e.features[0].properties.adcode;
const feature = this.adminFeatures.find(
(d) => d.properties.adcode === adcode
);
this.map.getSource("admin-children-boundry-h").setData(feature);
this.map.getCanvasContainer().style.cursor = "pointer";
});
this.map.on("mouseout", "admin-children-boundry-fill", (e) => {
this.map.getSource("admin-children-boundry-h").setData(new Geojson());
this.map.getCanvasContainer().style.cursor = "default";
});
},
initData() {
this.map.scrollZoom.disable();
this.map.doubleClickZoom.disable();
this.map.dragPan.disable();
this.map.dragRotate.disable();
fetch(`/gansu-b.geojson`)
.then((res) => res.json())
.then((geojson) => {
this.setBoundry(geojson.features);
this.fit2Geojson(geojson);
});
fetch(`/gansu-c.geojson`)
.then((res) => res.json())
.then((geojson) => {
this.adminFeatures = geojson.features;
this.map.getSource("admin-children-boundry").setData(geojson);
this.registerEvent()
});
},
mapLoaded(map) {
this.map = map;
this.initData();
},
fit2Geojson(geojson) {
const [xmin, ymin, xmax, ymax] = turf.bbox(geojson);
const bbox = [
[xmin, ymin],
[xmax, ymax],
];
const padding = 100;
const options = {
padding: {
top: padding,
bottom: padding,
left: padding,
right: padding,
},
duration: 100,
};
this.map.fitBounds(bbox, options);
},
},
};
</script>
<style scoped lang="scss">
.map {
width: 100%;
height: 100%;
}
</style>
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