如何绘制缩放时不会改变的虚线
How to draw dashed line which wouldn't be changing when scaling
当我用 'line-dasharray' 属性 绘制虚线时，它表现得很奇怪 - 缩放时线的长度和间隙会发生变化。请参阅示例。问题：如何绘制具有恒定线和间隙长度的虚线，当我缩放 in/out 时，它不会改变？
//这个愚蠢的机器人说我的 post 主要是代码。不知道有什么问题，
//但必须添加一些愚蠢的文本行
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
"paint": {
"line-color": "#888",
"line-width": 8,
"line-dasharray": [5, 5]
}
});
});
</script>
</body>
</html>
好吧，我发现了一些让它变得更好的东西，但它仍然不完美，因为虚线随着缩放不断变化。
部分答案是线之间的间隙以线宽单位而不是像素为单位指定。当线宽恒定（以像素为单位）并且不依赖于缩放时，它的大小（例如，以米为单位）会随着缩放级别的变化而变大或变小。这也会导致线条之间的间隙发生变化。 Here 您可以找到有关如何制作宽度可变的线条的说明，这将取决于缩放级别并保持其相对大小。
这是我将这种方法应用到我的示例中的结果（它变得更好，但当我缩小 in/zoom 时行仍然会发生变化）：
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
let baseWidth = 5;
let baseZoom = 15;
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
"paint": {
"line-color": "#888",
"line-width":
{
'type': 'exponential',
'base': 2,
'stops': [
[0, baseWidth * Math.pow(2, (0 - baseZoom))],
[22, baseWidth * Math.pow(2, (22 - baseZoom))]
]
},
"line-dasharray": [5, 5]
}
});
});
</script>
</body>
</html>
通过调整实际的 dasharray 值，您可以获得更好的行为（在我看来）。通过使第一个值小于第二个值，例如 [0.2, 2]，缩放更有意义。这是他们在 mapbox-gl-draw 库中使用的。
编辑：这是它的样子：
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
layout: {
'line-join': 'round',
'line-cap': 'round',
},
"paint": {
"line-color": "#888",
"line-width": 8,
"line-dasharray": [0.2, 2]
}
});
});
</script>
</body>
</html>
当我用 'line-dasharray' 属性 绘制虚线时，它表现得很奇怪 - 缩放时线的长度和间隙会发生变化。请参阅示例。问题：如何绘制具有恒定线和间隙长度的虚线，当我缩放 in/out 时，它不会改变？
//这个愚蠢的机器人说我的 post 主要是代码。不知道有什么问题，
//但必须添加一些愚蠢的文本行
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
"paint": {
"line-color": "#888",
"line-width": 8,
"line-dasharray": [5, 5]
}
});
});
</script>
</body>
</html>
好吧，我发现了一些让它变得更好的东西，但它仍然不完美，因为虚线随着缩放不断变化。
部分答案是线之间的间隙以线宽单位而不是像素为单位指定。当线宽恒定（以像素为单位）并且不依赖于缩放时，它的大小（例如，以米为单位）会随着缩放级别的变化而变大或变小。这也会导致线条之间的间隙发生变化。 Here 您可以找到有关如何制作宽度可变的线条的说明，这将取决于缩放级别并保持其相对大小。
这是我将这种方法应用到我的示例中的结果（它变得更好，但当我缩小 in/zoom 时行仍然会发生变化）：
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
let baseWidth = 5;
let baseZoom = 15;
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
"paint": {
"line-color": "#888",
"line-width":
{
'type': 'exponential',
'base': 2,
'stops': [
[0, baseWidth * Math.pow(2, (0 - baseZoom))],
[22, baseWidth * Math.pow(2, (22 - baseZoom))]
]
},
"line-dasharray": [5, 5]
}
});
});
</script>
</body>
</html>
通过调整实际的 dasharray 值，您可以获得更好的行为（在我看来）。通过使第一个值小于第二个值，例如 [0.2, 2]，缩放更有意义。这是他们在 mapbox-gl-draw 库中使用的。
编辑：这是它的样子：
<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8' />
<title>Add a GeoJSON line</title>
<meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.44.1/mapbox-gl.css' rel='stylesheet' />
<style>
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
</style>
</head>
<body>
<div id='map'></div>
<script>
mapboxgl.accessToken = 'pk.eyJ1IjoibHVjYXN3b2oiLCJhIjoiY2l5Nmg4cWU1MDA0ejMzcDJtNHJmZzJkcyJ9.WhcEdTYQH6sSw2pm0RSP9Q';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [-122.486052, 37.830348],
zoom: 15
});
map.on('load', function () {
map.addLayer({
"id": "route",
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
]
}
}
},
layout: {
'line-join': 'round',
'line-cap': 'round',
},
"paint": {
"line-color": "#888",
"line-width": 8,
"line-dasharray": [0.2, 2]
}
});
});
</script>
</body>
</html>