结合d3.js实现气象数据的可视化

{
    "header": {
        "la1": 54,
        "lo1": 73,
        "la2": 18,
        "lo2": 136,
        "nx": 630,
        "ny": 360
    },
    "data": [
        ......
    ]
}

var url = '../data/aqi.json';
console.time('timer');
$.ajax({
    type : "get",
    url : url,
    async : false,
    success : function(res){
        res = res[0];
        var header = res.header,
            data = res.data;
        var width = header.nx;
        var height = header.ny;
        if (!canvas) {
            canvas = document.createElement('canvas');
            canvas.setAttribute('id', 'canvas-layer');
            map.getCanvasContainer().appendChild(canvas);
            context = canvas.getContext('2d');
            //设置canvas透明度
            canvas.width = width;
            canvas.height = height;
            context.clearRect(0, 0, width, height);
        }
        canvas.style.display = 'block';
        var d3Path = d3.geoPath(null, context); //绘图笔
        //绘图登高线图
        var contours = d3.contours()
            .size([header.nx, header.ny])
            .thresholds(d3.range(0, 300, 5))(data);
        contours.forEach(function(geometry) {
            context.beginPath();
            d3Path(geometry);
            var v = geometry.value;
            var acolor = that.getColor(v);
            context.fillStyle = acolor;
            context.fill();
            context.strokeStyle = acolor;
            context.stroke();
        });
        var source = map.getSource('canvas-source');
        if(source) {
            map.removeLayer('canvas-layer');
            map.removeSource('canvas-source');
        }
        map.addSource('canvas-source', {
            type: 'canvas',
            canvas: 'canvas-layer',
            coordinates: [
                [header.lo1, header.la1],
                [header.lo2, header.la1],
                [header.lo2, header.la2],
                [header.lo1, header.la2]
            ],
            animate: true
        });
        map.addLayer({
            id: 'canvas-layer',
            type: 'raster',
            source: 'canvas-source',
            'paint': {
                'raster-opacity': 0.65,
                'raster-fade-duration': 0
            }
        });
        canvas.style.display = 'none';
        console.timeEnd('timer');
    }
});