概述

mapboxGl中多图标的实现可以在style中指定sprite来实现，但是在实际使用的时候会出现sprite之外的图标需要引用，此时通过map.addImage()来实现，但是如果存在多个图标的时候，因为map.addImage()需要先通过map.loadImage()先加载图标，而map.loadImage()是一个异步的，使用起来就有点麻烦。本文希望通过再再加sprite来实现一次性添加图标。

实现效果

image.png

实现

测试的sprite如下图：

merge.png
json文件如下：

{
"zgyh":{"visible":"true","pixelRatio":1,"x":0,"width":32,"y":105,"height":32},
"jsyh":{"visible":"true","pixelRatio":1,"x":0,"width":32,"y":35,"height":32},
"nyyh":{"visible":"true","pixelRatio":1,"x":0,"width":32,"y":70,"height":32},
"gsyh":{"visible":"true","pixelRatio":1,"x":0,"width":32,"y":0,"height":32}
}

实现代码如下：

  map.on('load',() => {
      const canvas = document.createElement('canvas')
      const ctx = canvas.getContext('2d')
      const img = new Image()
      img.src = './lib/merge.png'
      img.onload =  async () => {
        canvas.width = img.width
        canvas.height = img.height
        ctx.drawImage(img, 0, 0)
        fetch('./lib/merge.json').then(res => res.json()).then(res => {
          for (const k in res) {
            const { width, height, x, y } = res[k]
            const data = ctx.getImageData(x, y, width, height).data
            map.addImage(k, { width, height, data })
          }
          map.addSource('points', {
            type: 'geojson',
            data: {
              type: 'FeatureCollection',
              features: [
                {
                  "type": "Feature",
                  "properties": { icon: 'zgyh' },
                  "geometry": { "type": "Point", "coordinates": [107.0132554, 22.1441921] }
                },
                {
                  "type": "Feature",
                  "properties": { icon: 'jsyh' },
                  "geometry": { "type": "Point", "coordinates": [107.0223554, 22.1443921] }
                },
                {
                  "type": "Feature",
                  "properties": { icon: 'nyyh' },
                  "geometry": { "type": "Point", "coordinates": [107.0344554, 22.1444921] }
                }
              ]
            }

          });
          map.addLayer({
            'id': 'points-h',
            'type': 'symbol',
            'source': 'points',
            'layout': {
              'icon-allow-overlap': true,
              'icon-image': ['get', 'icon'],
              'icon-size': [
                "interpolate",
                [
                  "exponential",
                  1.5
                ],
                [
                  "zoom"
                ],
                5, 0.5,
                10, 0.8
              ]
            },
          });
        })
      }
    })