javascript - 如何为 svg 路径的渐进式绘图设置动画？

Question

我想仅使用带有 svg/canvas 和 js maximum 的 css 为线条的渐进式绘图设置动画。可以找到我想画的线的想法 here

<svg width="640" height="480" xmlns="http://www.w3.org/2000/svg">
 <!-- Created with SVG-edit - http://svg-edit.googlecode.com/ -->
 <g>
  <title>Layer 1</title>
  <path d="m33,104c1,0 2.1306,-0.8037 23,3c9.07012,1.65314 10,2 24,2c7,0 29,0 33,0c8,0 9,0 11,0c2,0 8,0 11,0c9,0 17,0 18,0c10,0 12,0 20,0c1,0 6,0 7,0c2,0 3.07613,0.38268 4,0c2.61313,-1.08239 2,-3 2,-6c0,-1 0,-2 0,-3c0,-1 0,-2 0,-3c0,-1 0,-2 0,-3c0,-1 0.30745,-3.186 -1,-5c-0.8269,-1.14727 -0.09789,-2.82443 -2,-4c-0.85065,-0.52573 -2.82443,-0.09789 -4,-2c-0.52573,-0.85065 -2.58578,-0.58578 -4,-2c-0.70711,-0.70711 -1.81265,-1.20681 -4,-3c-2.78833,-2.28588 -3.64749,-2.97251 -8,-4c-2.91975,-0.68926 -4.82375,-2.48626 -7,-3c-2.91975,-0.68926 -5.15224,-0.23463 -7,-1c-1.30656,-0.5412 -4.38687,-1.91761 -7,-3c-1.84776,-0.76537 -5.03609,0.37821 -7,0c-5.28799,-1.01837 -8,-3 -9,-3c-2,0 -5.0535,-0.54049 -7,-1c-2.17625,-0.51374 -4.15224,-0.23463 -6,-1c-1.30656,-0.54119 -3,-1 -4,-1c-2,0 -5,-1 -6,-1c-1,0 -3,-2 -6,-2c-2,0 -5,-2 -6,-2c-2,0 -2.02583,-0.67963 -4,-1c-3.12144,-0.50654 -4.15224,-0.23463 -6,-1c-1.30656,-0.54119 -2,-1 -3,-1c-2,0 -3,0 -5,0c-1,0 -2,0 -3,0c-1,0 -2,0 -3,0c-1,0 -2,0 -3,0c-2,0 -3.85273,0.1731 -5,1c-1.81399,1.30745 -5.18601,1.69255 -7,3c-1.14727,0.8269 -1.82375,2.48626 -4,3c-0.97325,0.22975 -1.69344,1.45881 -3,2c-0.92388,0.38268 -1.45951,1.0535 -1,3c0.51374,2.17625 3.07844,2.78985 6,4c2.06586,0.85571 3.38688,1.91761 6,3c1.84776,0.76537 5.2987,-1.05146 7,0c1.90211,1.17557 3.82375,2.48626 6,3c0.97325,0.22975 3.29289,0.29289 4,1c0.70711,0.70711 4,2 9,4c5,2 8,4 11,4c2,0 5,0 7,0c3,0 5,0 7,0c2,0 4,0 7,0c2,0 4,0 8,0c3,0 7,0 10,0c4,0 7,0 12,0c3,0 5,0 6,0c2,0 3,0 5,0c1,0 1.09789,-0.82443 3,-2c0.85065,-0.52573 3.07613,0.38268 4,0c1.30656,-0.5412 0.71022,-2.04291 1,-3c1.04483,-3.45084 2.84723,-5.04132 4,-9c0.88414,-3.03616 1.85194,-5.22836 3,-8c0.5412,-1.30656 1.5405,-2.0535 2,-4c0.51375,-2.17625 2.71413,-4.21167 5,-7c2.68979,-3.28101 4,-6 5,-7c1,-1 2,-2 2,-4c0,-1 0.70711,-2.29289 0,-3c-0.70711,-0.70711 -2.07613,0.38268 -3,0c-1.30656,-0.54119 -2,-1 -4,-1c-3,0 -6.87856,-2.49346 -10,-3c-2.96126,-0.48055 -6.71201,-0.98162 -12,-2c-2.94586,-0.56732 -5,-1 -9,-1c-3,0 -6,-1 -8,-1c-2,0 -5,-3 -7,-3c-2,0 -5.38687,-0.91761 -8,-2c-0.92388,-0.38268 -3.0535,-0.54049 -5,-1c-2.17625,-0.51374 -4.58578,0.41421 -6,-1c-0.70711,-0.70711 -1,-1 -2,-1c-1,0 -2,0 -3,0c-1,0 -2,0 -4,0c-1,0 -2,0 -3,0c-1,0 -2,0 -4,0c-1,0 -2,0 -3,0c-2,0 -3,0 -5,0c-1,0 -2,0 -3,0c-1,0 -3,0 -4,0c-3,0 -5,0 -7,0c-2,0 -4,0 -6,0c-2,0 -3,0 -5,0c-1,0 -2,0 -3,0c-2,0 -4,0 -5,0c-1,0 -2,0 -4,0c-1,0 -2,0 -3,1l-1,0" id="svg_1" stroke-width="5" stroke="#000000" fill="none"/>
 </g>
</svg>

Answer 1

此答案中列出了三种技术:

---

有一个全 SVG 解决方案，涉及逐步修改形状的 stroke-dasharray 以绘制越来越长的“破折号”，然后是一个巨大的间隙。

演示:http://phrogz.net/svg/progressively-drawing-svg-path-via-dasharray.html

相关代码:

var distancePerPoint = 1;
var drawFPS          = 60;

var orig = document.querySelector('path'), length, timer;
orig.addEventListener('mouseover',startDrawingPath,false);
orig.addEventListener('mouseout', stopDrawingPath, false);

function startDrawingPath(){
  length = 0;
  orig.style.stroke = '#f60';
  timer = setInterval(increaseLength,1000/drawFPS);
}

function increaseLength(){
  var pathLength = orig.getTotalLength();
  length += distancePerPoint;
  orig.style.strokeDasharray = [length,pathLength].join(' ');
  if (length >= pathLength) clearInterval(timer);
}

function stopDrawingPath(){
  clearInterval(timer);
  orig.style.stroke = '';
  orig.style.strokeDasharray = '';
}

---

或者，您仍然可以使用所有 SVG 并选择一次一个命令构建 SVG 路径:

演示:http://phrogz.net/svg/progressively-cloning-svg-path.html

相关代码:

// Assumes 'orig' and dup' are SVG paths
function addNextPathSegment(){
  var nextIndex   = dup.pathSegList.numberOfItems;
  if (nextIndex<orig.pathSegList.numberOfItems){
    var nextSegment = orig.pathSegList.getItem(nextIndex);
    var segmentDup  = cloneSVGPathSeg( dup, nextSegment );
    dup.pathSegList.appendItem( segmentDup );
  }
}

function cloneSVGPathSeg( path, seg ){
  switch(seg.pathSegTypeAsLetter){
    case 'M': return path.createSVGPathSegMovetoAbs(seg.x,seg.y);                                                     break;
    case 'm': return path.createSVGPathSegMovetoRel(seg.x,seg.y);                                                     break;
    case 'L': return path.createSVGPathSegLinetoAbs(seg.x,seg.y);                                                     break;
    case 'l': return path.createSVGPathSegLinetoRel(seg.x,seg.y);                                                     break;
    case 'H': return path.createSVGPathSegLinetoHorizontalAbs(seg.x);                                                 break;
    case 'h': return path.createSVGPathSegLinetoHorizontalRel(seg.x);                                                 break;
    case 'V': return path.createSVGPathSegLinetoVerticalAbs(seg.y);                                                   break;
    case 'v': return path.createSVGPathSegLinetoVerticalRel(seg.y);                                                   break;
    case 'C': return path.createSVGPathSegCurvetoCubicAbs(seg.x,seg.y,seg.x1,seg.y1,seg.x2,seg.y2);                   break;
    case 'c': return path.createSVGPathSegCurvetoCubicRel(seg.x,seg.y,seg.x1,seg.y1,seg.x2,seg.y2);                   break;
    case 'S': return path.createSVGPathSegCurvetoCubicSmoothAbs(seg.x,seg.y,seg.x2,seg.y2);                           break;
    case 's': return path.createSVGPathSegCurvetoCubicSmoothRel(seg.x,seg.y,seg.x2,seg.y2);                           break;
    case 'Q': return path.createSVGPathSegCurvetoQuadraticAbs(seg.x,seg.y,seg.x1,seg.y1);                             break;
    case 'q': return path.createSVGPathSegCurvetoQuadraticRel(seg.x,seg.y,seg.x1,seg.y1);                             break;
    case 'T': return path.createSVGPathSegCurvetoQuadraticSmoothAbs(seg.x,seg.y);                                     break;
    case 't': return path.createSVGPathSegCurvetoQuadraticSmoothRel(seg.x,seg.y);                                     break;
    case 'A': return path.createSVGPathSegArcAbs(seg.x,seg.y,seg.r1,seg.r2,seg.angle,seg.largeArcFlag,seg.sweepFlag); break;
    case 'a': return path.createSVGPathSegArcRel(seg.x,seg.y,seg.r1,seg.r2,seg.angle,seg.largeArcFlag,seg.sweepFlag); break;
    case 'z':
    case 'Z': return path.createSVGPathSegClosePath();                                                                break;
  }
}

---

最后，您可以选择通过定期采样 SVG 路径并绘制到 Canvas 来将路径绘制到 HTML5 Canvas 。 (请注意，不需要显示 SVG 路径即可发生这种情况；您可以完全在 JavaScript 中构建 SVG 路径元素并对其进行采样):

演示:http://phrogz.net/svg/progressively-drawing-svg-path.html

相关代码:

function startDrawingPath(){
  points = [];
  timer = setInterval(buildPath,1000/drawFPS);
}

// Assumes that 'orig' is an SVG path
function buildPath(){
  var nextPoint = points.length * distancePerPoint;
  var pathLength = orig.getTotalLength();
  if (nextPoint <= pathLength){
    points.push(orig.getPointAtLength(nextPoint));
    redrawCanvas();
  } else stopDrawingPath();
}

function redrawCanvas(){
  clearCanvas();
  ctx.beginPath();
  ctx.moveTo(points[0].x,points[0].y);
  for (var i=1;i<points.length;i++) ctx.lineTo(points[i].x,points[i].y);
  ctx.stroke();
}