SVG 的每个路径命令的手动动画

Question

是否可以为 每个path command 手动（使用按钮）而不是连续地在 SVG 的绘图属性上制作动画？

.path {stroke-dasharray: 1000;
       stroke-dashoffset: 1000;
       animation: dash 5s linear alternate infinite;}
@keyframes dash {from {stroke-dashoffset: 822;}
                 to   {stroke-dashoffset: 0;}
                 }

<svg width="200" height="200" viewBox="50 50 240 270">
  <path class="path" fill="white" stroke="black" stroke-width="4" 
        d="M66.039,133.545c0,0-21-57,18-67s49-4,65,8 s30,41,53,27s66,4,58,32s-5,44,18,57s22,46,0,
           45s-54-40-68-16s-40,88-83,48s11-61-11-80s-79-7-70-41 C46.039,146.545,53.039,128.545,66.039,133.545z"/>
</svg>

这可以帮助合并两个或多个路径命令并减少 SVG 中绘制路径命令的数量。

Answer 1

您需要获取每个路径段的长度，因为您正在动画/转换stroke-dasharray/stroke-dashoffset 值。

这是一个简化的示例，它使用的路径显示了一个周长为 100（直径=31,832 * π）的正圆。路径由 4 段组成，段长度应为 25 个单位。

获取所有段长度的辅助函数基于 @bez997's answer

let svg = document.querySelector("svg");
let path = svg.querySelector(".path");
let pathLength = path.getTotalLength().toFixed(1) * 1;

/**
 * save segments' path lengths to array
 **/

let segments = getSegmentLengths(path);
let segmentJson = JSON.stringify(segments).replaceAll('"', "");

/**
* @bez997
https://stackoverflow.com/questions/21564905/svg-api-length-of-a-single-segment#answer-45793408
original pen: https://codepen.io/bez997/pen/dzJemZ?editors=1010
**/

function getSegmentLengths(path) {
  let segList = path.pathSegList;
  // temporary path for computing segments
  let lengthPath = document.createElementNS(
    "http://www.w3.org/2000/svg",
    "path"
  );
  let lastLength = 0;
  let segLengths = [];
  let segSteps = [];
  let segOffset = 0;

  for (let i = 0; i < segList.numberOfItems; i += 1) {
    let segObj = segList.getItem(i);
    lengthPath.pathSegList.appendItem(segObj);
    // rounding numbers
    let currentLength = lengthPath.getTotalLength().toFixed(1) * 1;
    let segmentLength = (currentLength - lastLength).toFixed(1) * 1;

    // strip M and Z commands since, they don't have any length
    if (segmentLength) {
      lastLength = currentLength;
      segSteps.push({
        offset: i == 1 ? 0 : -(lastLength - segmentLength).toFixed(1) * 1,
        dash: segmentLength,
        currentLength: currentLength
      });
    }
  }
  return segSteps;
}

/**
 * change stroke dash attributes for animation
 **/
function strokeTo(path, pathLength, offset, dash) {
  let gap = pathLength - dash;
  path.setAttribute("stroke-dashoffset", offset);
  path.setAttribute("stroke-dasharray", dash + " " + gap);
}

/**
 * create navigation for each segment
 **/
function getStrokeNav(svg, segments, singleSegment = true, label = "") {
  let strokeNav = label;
  let index = 0;
  segments.forEach(function (el, i) {
    index++;
    let thisOffset = el.offset;
    let thisDash = el.dash;

    if (!singleSegment) {
      thisOffset = 0;
      thisDash = el.currentLength;
    }
    strokeNav +=
      '<button type="button" onclick="strokeTo(path,' +
      pathLength +
      ", " +
      thisOffset +
      ", " +
      thisDash +
      ')">' +
      index +
      "</button>";
  });

  return strokeNav;
}

// nav html output
let strokeToNav =
  "<p>" +
  getStrokeNav(svg, segments, false, "Animate to stroke segment ") +
  "</p><p>" +
  getStrokeNav(svg, segments, true, "Animate single segment ") +
  "</p>";
document.body.insertAdjacentHTML("afterBegin", strokeToNav);

svg {
  border: 1px solid #ccc;
  display: inline-block;
  font-size: calc( ( 25vw + 25vh )/ 2) ;
  width: 1em;
}

.path{
  transition:0.5s
}

<script src="https://cdn.rawgit.com/progers/pathseg/a1072a7b/pathseg.js"></script>
<svg  id="svg" xmlns="http://www.w3.org/2000/svg" 
      viewBox="0 0 50 50" >
<path class="path" fill="none" stroke="#000"  d="
M40.916,25
c0,8.79-7.125,15.916-15.916,15.916
S9.084,33.79,9.084,25
S16.21,9.084,25,9.084
S40.916,16.21,40.916,25
z" />
</svg>

预期的段数组将是：

let segments = [
  {offset:0, dash:25, currentLength:25},
  {offset:-25, dash:25, currentLength:50},
  {offset:-50, dash:25, currentLength:75},
  {offset:-75, dash:25, currentLength:100}
];

通过还保存一个偏移值，我们可以过渡到一个片段（包括以前的片段），但也可以为单个片段设置动画。

stroke-dashoffset="0" stroke-dasharray="25 75"

将显示第一个（右下）分段笔划。

一旦你得到了所有的段，你就可以将这些数据静态地存储到一个数组或 json 中。由于长度计算会创建一个临时 DOM 元素，因此您可能会遇到一些性能损失，具体取决于 svg 的复杂性。

let svg = document.querySelector("svg");
let path = svg.querySelector(".path");
let pathLength = path.getTotalLength().toFixed(1) * 1;

/**
 * save segments' path lengths to array
 **/
let segments = [
  { offset: 0, dash: 78.6, currentLength: 78.6 },
  { offset: -78.6, dash: 68.8, currentLength: 147.4 },
  { offset: -147.4, dash: 65.1, currentLength: 212.5 },
  { offset: -212.5, dash: 81.9, currentLength: 294.4 },
  { offset: -294.4, dash: 66.3, currentLength: 360.7 },
  { offset: -360.7, dash: 61.4, currentLength: 422.1 },
  { offset: -422.1, dash: 76.5, currentLength: 498.6 },
  { offset: -498.6, dash: 116.9, currentLength: 615.5 },
  { offset: -615.5, dash: 89.3, currentLength: 704.8 },
  { offset: -704.8, dash: 90.2, currentLength: 795 },
  { offset: -795, dash: 26.6, currentLength: 821.6 }
];


/**
 * change stroke dash attributes for animation
 **/
function strokeTo(path, pathLength, offset, dash) {
  let gap = pathLength - dash;
  path.setAttribute("stroke-dashoffset", offset);
  path.setAttribute("stroke-dasharray", dash + " " + gap);
}

svg {
  border: 1px solid #ccc;
  display: inline-block;
  font-size: calc( ( 50vw + 50vh )/ 2) ;
  width: 1em;
}

.path{
  transition:0.5s
}

<svg width="200" height="200" viewBox="50 50 240 270">
  <path class="path" fill="white" stroke="black" stroke-width="4" 
        d="M66.039,133.545c0,0-21-57,18-67s49-4,65,8 s30,41,53,27s66,4,58,32s-5,44,18,57s22,46,0,
           45s-54-40-68-16s-40,88-83,48s11-61-11-80s-79-7-70-41 C46.039,146.545,53.039,128.545,66.039,133.545z"/>
</svg>

<p>Animate to stroke segment <button type="button" onclick="strokeTo(path,821.6, 0, 78.6)">1</button><button type="button" onclick="strokeTo(path,821.6, 0, 147.4)">2</button><button type="button" onclick="strokeTo(path,821.6, 0, 212.5)">3</button><button type="button" onclick="strokeTo(path,821.6, 0, 294.4)">4</button><button type="button" onclick="strokeTo(path,821.6, 0, 360.7)">5</button><button type="button" onclick="strokeTo(path,821.6, 0, 422.1)">6</button><button type="button" onclick="strokeTo(path,821.6, 0, 498.6)">7</button><button type="button" onclick="strokeTo(path,821.6, 0, 615.5)">8</button><button type="button" onclick="strokeTo(path,821.6, 0, 704.8)">9</button><button type="button" onclick="strokeTo(path,821.6, 0, 795)">10</button><button type="button" onclick="strokeTo(path,821.6, 0, 821.6)">11</button></p>

<p>Animate single segment <button type="button" onclick="strokeTo(path,821.6, 0, 78.6)">1</button><button type="button" onclick="strokeTo(path,821.6, -78.6, 68.8)">2</button><button type="button" onclick="strokeTo(path,821.6, -147.4, 65.1)">3</button><button type="button" onclick="strokeTo(path,821.6, -212.5, 81.9)">4</button><button type="button" onclick="strokeTo(path,821.6, -294.4, 66.3)">5</button><button type="button" onclick="strokeTo(path,821.6, -360.7, 61.4)">6</button><button type="button" onclick="strokeTo(path,821.6, -422.1, 76.5)">7</button><button type="button" onclick="strokeTo(path,821.6, -498.6, 116.9)">8</button><button type="button" onclick="strokeTo(path,821.6, -615.5, 89.3)">9</button><button type="button" onclick="strokeTo(path,821.6, -704.8, 90.2)">10</button><button type="button" onclick="strokeTo(path,821.6, -795, 26.6)">11</button></p>

作为替代方案，您也可以将细分存储在 svg 数据属性中 - 尽管数据属性仍然不符合规范。
但是，它们不应引入渲染问题。

这种方法的一个好处是，您的分段数据可以直接保存在您的 svg 标记/文件中，同时减少您的 js 文件。

let svg = document.querySelector("svg");
let path = svg.querySelector(".path");
let pathLength = path.getTotalLength().toFixed(1)*1;


/**
* change stroke dash attributes for animation
**/
function strokeTo(path, pathLength, offset, dash) {
  let gap = pathLength - dash;
  path.setAttribute("stroke-dashoffset", offset);
  path.setAttribute("stroke-dasharray", dash + " " + gap);
}

svg {
  border: 1px solid #ccc;
  display: inline-block;
  font-size: calc( ( 50vw + 50vh )/ 2) ;
  width: 1em;
}

.path{
  transition:0.3s
}

<svg width="200" height="200" viewBox="50 50 240 270" data-segments='[{"offset":0,"dash":78.6,"currentLength":78.6},{"offset":-78.6,"dash":68.8,"currentLength":147.4},{"offset":-147.4,"dash":65.1,"currentLength":212.5},{"offset":-212.5,"dash":81.9,"currentLength":294.4},{"offset":-294.4,"dash":66.3,"currentLength":360.7},{"offset":-360.7,"dash":61.4,"currentLength":422.1},{"offset":-422.1,"dash":76.5,"currentLength":498.6},{"offset":-498.6,"dash":116.9,"currentLength":615.5},{"offset":-615.5,"dash":89.3,"currentLength":704.8},{"offset":-704.8,"dash":90.2,"currentLength":795},{"offset":-795,"dash":26.6,"currentLength":821.6}]'>
  <path class="path" fill="white" stroke="black" stroke-width="4" d="M66.039,133.545c0,0-21-57,18-67s49-4,65,8 s30,41,53,27s66,4,58,32s-5,44,18,57s22,46,0,
           45s-54-40-68-16s-40,88-83,48s11-61-11-80s-79-7-70-41 C46.039,146.545,53.039,128.545,66.039,133.545z"></path>
</svg>


<p>Animate single segment <button type="button" onclick="strokeTo(path,821.6, 0, 78.6)">1</button><button type="button" onclick="strokeTo(path,821.6, -78.6, 68.8)">2</button><button type="button" onclick="strokeTo(path,821.6, -147.4, 65.1)">3</button><button type="button" onclick="strokeTo(path,821.6, -212.5, 81.9)">4</button><button type="button" onclick="strokeTo(path,821.6, -294.4, 66.3)">5</button><button type="button" onclick="strokeTo(path,821.6, -360.7, 61.4)">6</button><button type="button" onclick="strokeTo(path,821.6, -422.1, 76.5)">7</button><button type="button" onclick="strokeTo(path,821.6, -498.6, 116.9)">8</button><button type="button" onclick="strokeTo(path,821.6, -615.5, 89.3)">9</button><button type="button" onclick="strokeTo(path,821.6, -704.8, 90.2)">10</button><button type="button" onclick="strokeTo(path,821.6, -795, 26.6)">11</button></p>