Convert SVG Path to All-Absolute Commands: JavaScript code to modify an SVG path in-place for simpler usage.

posted 2012-Mar-12

SVG Path data can have a mix of absolute commands (“go to x,y”) and relative commands (“go left 10 more than wherever you are”). Sometimes it’s nice to have your SVG path using only absolute commands. Following is a JavaScript function that takes an SVG Path element and converts all relative commands in place to the absolute equivalent. Afterwards you can use developer tools to “Copy as HTML”, or use getAttribute('d'), or whatever.

function convertToAbsolute(path){
  var x0,y0,x1,y1,x2,y2,segs = path.pathSegList;
  for (var x=0,y=0,i=0,len=segs.numberOfItems;i<len;++i){
    var seg = segs.getItem(i), c=seg.pathSegTypeAsLetter;
    if (/[MLHVCSQTA]/.test(c)){
      if ('x' in seg) x=seg.x;
      if ('y' in seg) y=seg.y;
    }else{
      if ('x1' in seg) x1=x+seg.x1;
      if ('x2' in seg) x2=x+seg.x2;
      if ('y1' in seg) y1=y+seg.y1;
      if ('y2' in seg) y2=y+seg.y2;
      if ('x'  in seg) x += seg.x;
      if ('y'  in seg) y += seg.y;
      switch(c){
        case 'm': segs.replaceItem(path.createSVGPathSegMovetoAbs(x,y),i);                   break;
        case 'l': segs.replaceItem(path.createSVGPathSegLinetoAbs(x,y),i);                   break;
        case 'h': segs.replaceItem(path.createSVGPathSegLinetoHorizontalAbs(x),i);           break;
        case 'v': segs.replaceItem(path.createSVGPathSegLinetoVerticalAbs(y),i);             break;
        case 'c': segs.replaceItem(path.createSVGPathSegCurvetoCubicAbs(x,y,x1,y1,x2,y2),i); break;
        case 's': segs.replaceItem(path.createSVGPathSegCurvetoCubicSmoothAbs(x,y,x2,y2),i); break;
        case 'q': segs.replaceItem(path.createSVGPathSegCurvetoQuadraticAbs(x,y,x1,y1),i);   break;
        case 't': segs.replaceItem(path.createSVGPathSegCurvetoQuadraticSmoothAbs(x,y),i);   break;
        case 'a': segs.replaceItem(path.createSVGPathSegArcAbs(x,y,seg.r1,seg.r2,seg.angle,seg.largeArcFlag,seg.sweepFlag),i);   break;
        case 'z': case 'Z': x=x0; y=y0; break;
      }
    }
    if (c=='M' || c=='m') x0=x, y0=y;
  }
}