如何从 SVG 路径的交集找到新路径（形状）？

Question

我需要相交 2 条 SVG 路径并获得与它们相交的路径。

它应该在浏览器或 Node.js 中工作（其中任何一个，而不是两者）。
我需要交集，clip-path 的用法不正确。
如果由于某种原因交集将使用 transform 没关系（我会自己删除它）。

我认为有一个库，但我只找到了

svg-intersections - returns 点数组，但我需要 path
path-intersection - 不能让它工作 - 由于某种原因它总是 returns 一个空数组
snap.svg - 似乎提供了一些有用的东西，但我不明白如何使用它
就像 Difference and Intersection of paths in SVG using Snap.path.intersection

例如相交以下路径：

M 24.379464,51.504463 23.434524,23.156249 38.742559,12.572916 c 0,0 29.860118,-9.0714281 17.00893,0.755953 -12.851191,9.82738 13.229166,19.465774 13.229166,19.465774 z
m 32.883928,0.28869028 c 0,0 -15.686011,1.51190452 -8.504463,7.18154712 7.181546,5.6696426 50.270836,30.0491076 26.458332,42.3333336 -23.8125,12.284226 47.058036,14.174107 47.058036,14.174107 z

我想要这样的东西：

M 43.943359 11.123047 C 40.995759 11.900151 38.742188 12.572266 38.742188 12.572266 L 35.236328 14.996094 C 44.091432999999995 21.21816 55.052161 29.822765 57.455078 37.628906 L 66.939453 33.650391 63.632812 30.410156 C 58.77426 27.95814 52.364322 23.85552 52.214844 19.224609 L 43.943359 11.123047 z

这是示例中带有 path 的交互式代码段（忽略颜色 - 为清楚起见）- 需要从 #path1 获取 Intersection 和#path2:

svg { width: 10em; width: 100vmin; outline: 1px dotted blue; display: none; }
input { display: none; }
label { width: 10em; float: left; clear: left; cursor: pointer; line-height: 2em; margin: 0 .5em .25em 0; padding: 0 .25em; border: 1px solid; }
:checked + * + * + label { background: antiquewhite; color: blue; }
:checked + * + * + * + * + * + svg { display: inline-block; }

<input type=radio name=svg id=in checked>
<input type=radio name=svg id=out>
<input type=radio name=svg id=cp>

<label for=in>Input</label>
<label for=out>Intersection</label>
<label for=cp>Clip</label>

<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" viewBox="22 0 76 64">
  <path id="path1"
    style="fill:rgba(255,0,0,.5); stroke:red;stroke-width:0.26458332px;"
    d="M 24.379464,51.504463 23.434524,23.156249 38.742559,12.572916 c 0,0 29.860118,-9.0714281 17.00893,0.755953 -12.851191,9.82738 13.229166,19.465774 13.229166,19.465774 z"
  />
  <path id="path2"
    style="fill:rgba(0,255,0,.5);stroke:green;stroke-width:0.26458332px;"
    d="m 32.883928,0.28869028 c 0,0 -15.686011,1.51190452 -8.504463,7.18154712 7.181546,5.6696426 50.270836,30.0491076 26.458332,42.3333336 -23.8125,12.284226 47.058036,14.174107 47.058036,14.174107 z"
  />
</svg>

<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" viewBox="22 0 76 64">
  <path
    style="fill:rgba(0,0,255,.5);stroke:blue;stroke-width:0.26458332px;"
    d="M 43.943359 11.123047 C 40.995759 11.900151 38.742188 12.572266 38.742188 12.572266 L 35.236328 14.996094 C 44.091432999999995 21.21816 55.052161 29.822765 57.455078 37.628906 L 66.939453 33.650391 63.632812 30.410156 C 58.77426 27.95814 52.364322 23.85552 52.214844 19.224609 L 43.943359 11.123047 z"
  />
</svg>

<svg xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="22 0 76 64">
  <clipPath id="clip2">
    <use xlink:href="#path2" />
  </clipPath>
  <use xlink:href="#path1" clip-path="url(#clip2)" />
</svg>

示例Snap.svg：

var p1 = "M 24.379464,51.504463 23.434524,23.156249 38.742559,12.572916 c 0,0 29.860118,-9.0714281 17.00893,0.755953 -12.851191,9.82738 13.229166,19.465774 13.229166,19.465774 z"
var p2 = "m 32.883928,0.28869028 c 0,0 -15.686011,1.51190452 -8.504463,7.18154712 7.181546,5.6696426 50.270836,30.0491076 26.458332,42.3333336 -23.8125,12.284226 47.058036,14.174107 47.058036,14.174107 z"

var intersection = Snap.path.intersection(p1, p2)

console.log(intersection)

.as-console-wrapper.as-console-wrapper { max-height: 100vh }

<script src=//cdnjs.cloudflare.com/ajax/libs/snap.svg/0.5.1/snap.svg-min.js></script>

PS: Same question in Russian.

Answer 1

Snap.svg 似乎具有执行此操作所需的基本功能。他们中的一些人有点尴尬，但这可能是前进的方向。请将此视为伪代码，而不是按原样工作：

// returns something like [ [ "M", 1, 2 ], ["C", 3, 4, 5, 6, 7, 8 ], ... ]
// and has a custom .toString() method
segList1 = Snap.path.toCubic(p1)
segList2 = Snap.path.toCubic(p2)

intersections = Snap.path.intersection(p1, p2)

// handle the subpaths between neighbouring intersections
intersectionPaths = intersections.map((point, id) => {
    from = point
    to = intersections[id + 1 < intersections.length ? id + 1 : 0]
    return pathBetweenIntersections(from, to)
})

// return the two paths between two neighbouring intersection points
function pathBetweenIntersections (from, to) {
    // list the segments between the intersection points on first path
    // TODO: handle cases when from.segment1 >= to.segment1
    subSegList1 = segList1.slice(from.segment1 + 1, to.segment1)

    // first segment has the intersection point
    startSegments = [ from.bez1.slice(0, 2).unshift('M'), from.bez1.slice(2, 8).unshift('C') ]
    startString1 = Snap.path.toCubic(startSegments).toString()
    // construct a path element from the segment
    startPath1 = Paper.path(startString1)
    startPathLength1 = startPath1.getTotalLength()
    // get the relevant subpath from intersection point to end
    startPathString1 = startPath1.getSubpath(from.t1 * startPathLength1, startPathLength1)
    subSegList1 = Snap.path.toCubic(startPathString1).concat(subSegList1)

    // and the same for the last segment
    endSegments = [ to.bez1.slice(0, 2).unshift('M'), to.bez1.slice(2, 8).unshift('C') ]
    endString1 = Snap.path.toCubic(endSegments).toString()
    endPath1 = Paper.path(endString1)
    endPathLength1 = endPath1.getTotalLength()
    endPathString1 = endPath1.getSubpath(0, to.t1 * endPathString1)
    subSegList1.push(Snap.path.toCubic(endPathString1)[1])

    subSegList2 = // do the same for segList2

    return {
        p1: Snap.path.toCubic(subSegList1).toString(),
        p2: Snap.path.toCubic(subSegList2).toString()
    }
}

Answer 2

我们可以使用 PaperJS 布尔运算来实现，它可以使用 SVG 路径进行运算。

PaperJS 有 5 种不同的布尔运算：exclude、subtract、unite、intersect、divide 我们将使用其中的一种姓名 intersect。此操作也是具有相同名称的函数，它们 return item 对象具有函数 exportSVG()。它 return 是正确的 SVG Path element，它具有两条路径相交的新形状。

正确解的例子

paper.install(window);
window.onload = function()
{
    paper.setup('canvas');

    var p1 = 'M 24.379464,51.504463 23.434524,23.156249 38.742559,12.572916 c 0,0 29.860118,-9.0714281 17.00893,0.755953 -12.851191,9.82738 13.229166,19.465774 13.229166,19.465774 z',
        p2 = 'm 32.883928,0.28869028 c 0,0 -15.686011,1.51190452 -8.504463,7.18154712 7.181546,5.6696426 50.270836,30.0491076 26.458332,42.3333336 -23.8125,12.284226 47.058036,14.174107 47.058036,14.174107 z',
        path1 = new Path(p1),
        path2 = new Path(p2);

    path1.fillColor = 'rgba(255,0,0,.5)';
    path1.position = new Point(25, 25);

    path2.fillColor = 'rgba(0,255,0,.5)';
    path2.position = new Point(40, 25);
    
    var result = path2.intersect(path1);
    result.selected = true;
    result.fillColor = '#77f';

    //exportSVG() docu: http://paperjs.org/reference/item/#exportsvg
    var svgPathElement = result.exportSVG(),
        dPath = svgPathElement.getAttribute('d');
    
    document.querySelector('path').setAttribute('d', dPath);

    var output = document.querySelector('#output');
    output.innerHTML = '<pre>' + dPath + '</pre>';
    output.innerHTML += '<xmp>' + svgPathElement.outerHTML + '</xmp>';
};

table
{
    margin-left:14px;
    padding-left:14px;
    border-left:1px solid gray;
    display:inline-block
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/paper.js/0.12.0/paper-full.min.js"></script>

<canvas id="canvas" width="75" height="75" resize></canvas>
<table><tr><td><b>Our new shape of both paths intersection in separate SVG:</b></td></tr>
<tr><td>
    <svg width="75" height="75" viewBox="0 0 75 75">
    <path fill="rgba(0,0,255,.5)" d=""/>
    </svg>
</td></tr></table>

<div id="output"></div>

有用链接：

如何从 SVG 路径的交集找到新路径（形状）？

How to find a new path (shape) from intersection of SVG paths?

javascript

svg

node.js

snap.svg