我正在研究一个地图项目，我们在其中使用OSM磁贴和d3-tile项目渲染地图。我正在尝试在其上放置标记。但是，projection（long，lat）返回的值怪异，从而将标记放错了位置，例如对于纽约为-0.4777943611111111111，-0.3832333211677277：
newyork = [-74.2605518, 40.6971478];
svg.selectAll("circle")
.data([newyork]).enter()
.append("circle")
.attr("cx", function (d) { console.log(projection(d)); return -projection(d)[0]; })
.attr("cy", function (d) { return -projection(d)[1]; })
. attr("r", "20px")
.attr("fill", "red")
下面的完整源代码
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
margin: 0;
}
</style>
<svg></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://unpkg.com/[email protected]/build/d3-tile.js"></script>
<script>
var tau = 2 * Math.PI;
var width = 960;
height = 500;
// Initialize the projection to fit the world in a 1×1 square centered at the origin.
var projection = d3.geoMercator()
.scale(1 / tau)
.translate([0, 0]);
var path = d3.geoPath()
.projection(projection);
var tile = d3.tile()
.size([width, height]);
var zoom = d3.zoom()
.on("zoom", zoomed);
var svg = d3.select("svg")
.attr("width", width)
.attr("height", height);
var raster = svg.append("g");
// Center at US
var center = projection([-98.5, 39.5]);
console.log("Center " + center[0]);
// Apply a zoom transform equivalent to projection.{scale,translate,center}.
svg.call(zoom)
.call(zoom.transform, d3.zoomIdentity
.translate(width / 2, height / 2)
.scale(1 << 12)
.translate(-center[0], -center[1]));
newyork = [-74.2605518, 40.6971478];
console.log(projection(newyork))
svg.selectAll("circle")
.data([newyork]).enter()
.append("circle")
.attr("cx", function (d) { console.log(projection(d)); return -projection(d)[0]; })
.attr("cy", function (d) { return -projection(d)[1]; })
. attr("r", "20px")
.attr("fill", "red")
function zoomed() {
var transform = d3.event.transform;
var tiles = tile
.scale(transform.k)
.translate([transform.x, transform.y])
();
var image = raster
.attr("transform", stringify(tiles.scale, tiles.translate))
.selectAll("image")
.data(tiles, function(d) {
return d;
});
image.exit().remove();
// enter:
var entered = image.enter().append("image");
// update:
image = entered.merge(image)
.attr('xlink:href', function(d) {
return 'http://' + 'abc' [d.y % 3] + '.tile.openstreetmap.org/' +
d.z + '/' + d.x + '/' + d.y + '.png';
})
.attr('x', function(d) {
return d.x * 256;
})
.attr('y', function(d) {
return d.y * 256;
})
.attr("width", 256)
.attr("height", 256);
}
function stringify(scale, translate) {
var k = scale / 256,
r = scale % 1 ? Number : Math.round;
return "translate(" + r(translate[0] * scale) + "," + r(translate[1] * scale) + ") scale(" + k + ")";
}
</script>
感谢您的帮助。谢谢！
对于任何寻找答案的人都在这里找到。：D3 cartography: lon/lat circles in wrong place on map (projection)
技巧是在缩放函数中转换圆：
function zoomed() {
...
vector
.attr("transform", transform)
.attr("r", 5/transform.k);
...
}