我試圖在每個path元素的中心顯示一個圖示，但它看起來不正確
我的代碼只是根據寬度和高度計算了中心點path
const center = {
x: (bbox.x - svg_box.x) bbox.width / 2,
y: (bbox.y - svg_box.y) bbox.height / 2,
}
JSFiddle
可以使用質心函式來改進嗎？還是使用d3？
我無法弄清楚如何使用 d3 找到現有路徑的質心。
謝謝
uj5u.com熱心網友回復：
D3 有兩種質心方法：arc.centroid和path.centroid（來自d3-geo），沒有一種方法可以像您在這里使用的那樣使用路徑元素。
但是，我們可以path.centroid用來獲取這些路徑的質心，但它非常笨拙，您最好創建自己的代碼。也就是說，我們可以遍歷每條路徑，獲取它的長度并設定一個虛擬 geoJSON 物件：
const pathLength = n[i].getTotalLength();
let index = 0;
const geoJSONObject = {
"type": "Polygon",
"coordinates": [
[]
]
};
然后，我們沿著路徑移動并填充 geoJSON 物件（這里 400/1237 只是計算視口值的快速方法，如果需要，可以使用適當的矩陣）...
while (index < pathLength) {
const point = n[i].getPointAtLength(index);
geoJSONObject.coordinates[0].push([point.x * (400 / 1237), point.y * (400 / 1232)]);
index = precision;
};
...最后我們將該物件傳遞給path.centroid：
const centroid = path.centroid(geoJSONObject);
這是該解決方案的代碼段：
顯示代碼片段
const controls = d3.select(".controls"),
path = d3.geoPath()
.projection(d3.geoIdentity()),
precision = 100;
d3.selectAll("path").each((_, i, n) => {
const pathLength = n[i].getTotalLength();
let index = 0;
const geoJSONObject = {
"type": "Polygon",
"coordinates": [
[]
]
};
while (index < pathLength) {
const point = n[i].getPointAtLength(index);
geoJSONObject.coordinates[0].push([point.x * (400 / 1237), point.y * (400 / 1232)]);
index = precision;
};
const centroid = path.centroid(geoJSONObject);
controls.append("div")
.style("left", centroid[0] "px")
.style("top", centroid[1] "px");
}).container {
position: relative;
display: inline-flex;
}
path {
outline: 1px solid #0F0;
}
.controls {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
.controls>div {
position: absolute;
width: 5px;
height: 5px;
background-color: red;
}<script src="https://d3js.org/d3.v7.min.js"></script>
<div class="container">
<div class="controls"></div>
<?xml version="1.0" encoding="utf-8"?>
<!-- Generator: Adobe Illustrator 25.4.0, SVG Export Plug-In . SVG Version: 6.00 Build 0) -->
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="400" x="0px" y="0px" viewBox="0 0 1237 1232" style="enable-background:new 0 0 1237 1232;" xml:space="preserve">
<style type="text/css">
.st1 {
fill: none;
stroke: #000000;
stroke-miterlimit: 10;
}
</style>
<g>
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