我正在尝试在d3.js中制作显示所有美国县的SVG地图。当您单击状态时，它会将viewBox转换为状态，并根据其在地球上的位置对其进行旋转，因此它不会成角度。
问题在于，它渲染所有路径时非常慢。有没有理由很难渲染SVG图形，我有什么办法可以解决它？
如果有人想窥视，我的代码就在这里：
<html>
<head>
<title>US Map</title>
<script src="http://d3js.org/d3.v5.min.js"></script>
<script src="https://d3js.org/topojson.v3.min.js"></script>
<style>
body {
margin: 0;
overflow: hidden;
}
svg {
width: 100vw;
height: 100vh;
}
path {
fill: #ccc;
stroke: black;
stroke-width: .2;
}
#borders {
fill: none;
stroke-width: .8;
}
</style>
</head>
<body>
<svg></svg>
<script>
var svg = d3.select("svg"),
projection = d3.geoAlbersUsa(),
path = d3.geoPath(projection);
d3.json("https://cdn.jsdelivr.net/npm/us-atlas@3/counties-10m.json").then(function(us){
var states = topojson.feature(us, us.objects.states),
borders = topojson.mesh(us, us.objects.states, (a,b) => a != b);
states.features.filter(d => ![60,66,69,72,78].includes(Number(d.id))).forEach(function(state){
svg.datum(state)
.append("g")
.attr("id", state.id)
.on("click", function(d){
var p = projection.invert(path.centroid(d));
projection.rotate([-p[0], -p[1]]);
svg.transition().duration(750)
.selectAll("path:not(#borders)")
.attr("d", path);
var [[x0,y0],[x1,y1]] = path.bounds(d);
svg.transition().duration(750)
.attr("viewBox", `${x0-5} ${y0-5} ${x1-x0+10} ${y1-y0+10}`)
.select("#borders")
.attr("d", path(borders));
})
.selectAll("path")
.data(topojson.feature(us, us.objects.counties).features.filter(d => d.id.slice(0,2) == state.id))
.enter().append("path")
.attr("id", d => d.id)
.attr("d", path);
});
svg.append("path")
.attr("id", "borders")
.attr("d", path(borders));
var box = svg.node().getBBox();
svg.attr("viewBox", `${box.x} ${box.y} ${box.width} ${box.height}`);
projection = d3.geoMercator().scale([1000]);
path.projection(projection);
});
</script>
</body>
</html>```
我尝试了不使用viewBox的缩放功能。与以前相比，点击转换的速度更快。
PFA的代码相同。希望这对您有用。
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>D3: Zoom in to reveal counties</title>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<script type="text/javascript" src="https://d3js.org/topojson.v3.min.js"></script>
<style>
svg {
width: 95vw;
height: 95vh;
}
.background {
fill: none;
pointer-events: all;
}
#states {
fill: #aaa;
}
#states .active {
display: none;
}
#state-borders {
fill: none;
stroke: black;
stroke-width: 1.5px;
stroke-linejoin: round;
stroke-linecap: round;
pointer-events: none;
}
.county-boundary {
fill: #ccc;
stroke: black;
stroke-width: .2px;
}
.county-boundary:hover,
.state:hover {
fill: #ccc;
}
</style>
</head>
<body>
<svg></svg>
<script type="text/javascript">
var margin = {
top: 10,
bottom: 10,
left: 10,
right:10
}, width = parseInt(d3.select('svg').style('width')),
width = width - margin.left - margin.right,
mapRatio = 0.45,
height = width * mapRatio,
active = d3.select(null);
var svg = d3.select('svg')
.attr('class', 'center-container')
.attr('height', height + margin.top + margin.bottom)
.attr('width', width + margin.left + margin.right);
svg.append('rect')
.attr('class', 'background center-container')
.attr('height', height + margin.top + margin.bottom)
.attr('width', width + margin.left + margin.right)
.on('click', clicked);
Promise.resolve(d3.json("https://cdn.jsdelivr.net/npm/us-atlas@3/counties-10m.json"))
.then(render);
var projection = d3.geoAlbersUsa()
.translate([width /2 , height / 2])
.scale(width);
var path = d3.geoPath()
.projection(projection);
var g = svg.append("g")
.attr('class', 'center-container center-items us-state')
.attr('transform', 'translate('+margin.left+','+margin.top+')')
.attr('width', width + margin.left + margin.right)
.attr('height', height + margin.top + margin.bottom)
function render(us) {
g.append("g")
.attr("id", "counties")
.selectAll("path")
.data(topojson.feature(us, us.objects.counties).features)
.enter().append("path")
.attr("d", path)
.attr("class", "county-boundary")
.on("click", clicked)
g.append("g")
.attr("id", "states")
.selectAll("path")
.data(topojson.feature(us, us.objects.states).features)
.enter().append("path")
.attr("d", path)
.attr("class", "state active")
.on("click", clicked);
g.append("path")
.datum(topojson.mesh(us, us.objects.states, function(a, b) { return a !== b; }))
.attr("id", "state-borders")
.attr("d", path);
}
function clicked(d) {
if (d3.select('.background').node() === this) return reset();
if (active.node() === this) return reset();
active.classed("active", false);
active = d3.select(this).classed("active", true);
var bounds = path.bounds(d),
dx = bounds[1][0] - bounds[0][0],
dy = bounds[1][1] - bounds[0][1],
x = (bounds[0][0] + bounds[1][0]) / 2,
y = (bounds[0][1] + bounds[1][1]) / 2,
scale = .1 / Math.max(dx / width, dy / height),
translate = [width / 2 - scale * x, height / 2 - scale * y];
g.transition()
.duration(750)
.style("stroke-width", 1.5 / scale + "px")
.attr("transform", "translate(" + translate + ")scale(" + scale + ")");
}
function reset() {
active.classed("active", false);
active = d3.select(null);
g.transition()
.delay(100)
.duration(750)
.style("stroke-width", "1.5px")
.attr('transform', 'translate('+margin.left+','+margin.top+')');
}
</script>
</body>
</html>