visualization-design/public/js/canvas2svg.js

/*!!
 *  Canvas 2 Svg v1.0.19
 *  A low level canvas to SVG converter. Uses a mock canvas context to build an SVG document.
 *
 *  Licensed under the MIT license:
 *  http://www.opensource.org/licenses/mit-license.php
 *
 *  Author:
 *  Kerry Liu
 *
 *  Copyright (c) 2014 Gliffy Inc.
 */

(function() {
  'use strict';

  var STYLES, ctx, CanvasGradient, CanvasPattern, namedEntities;

  //helper function to format a string
  function format(str, args) {
    var keys = Object.keys(args),
      i;
    for (i = 0; i < keys.length; i++) {
      str = str.replace(
        new RegExp('\\{' + keys[i] + '\\}', 'gi'),
        args[keys[i]]
      );
    }
    return str;
  }

  //helper function that generates a random string
  function randomString(holder) {
    var chars, randomstring, i;
    if (!holder) {
      throw new Error(
        'cannot create a random attribute name for an undefined object'
      );
    }
    chars = 'ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz';
    randomstring = '';
    do {
      randomstring = '';
      for (i = 0; i < 12; i++) {
        randomstring += chars[Math.floor(Math.random() * chars.length)];
      }
    } while (holder[randomstring]);
    return randomstring;
  }

  //helper function to map named to numbered entities
  function createNamedToNumberedLookup(items, radix) {
    var i,
      entity,
      lookup = {},
      base10,
      base16;
    items = items.split(',');
    radix = radix || 10;
    // Map from named to numbered entities.
    for (i = 0; i < items.length; i += 2) {
      entity = '&' + items[i + 1] + ';';
      base10 = parseInt(items[i], radix);
      lookup[entity] = '&#' + base10 + ';';
    }
    //FF and IE need to create a regex from hex values ie &nbsp; == \xa0
    lookup['\\xa0'] = '&#160;';
    return lookup;
  }

  //helper function to map canvas-textAlign to svg-textAnchor
  function getTextAnchor(textAlign) {
    //TODO: support rtl languages
    var mapping = {
      left: 'start',
      right: 'end',
      center: 'middle',
      start: 'start',
      end: 'end'
    };
    return mapping[textAlign] || mapping.start;
  }

  //helper function to map canvas-textBaseline to svg-dominantBaseline
  function getDominantBaseline(textBaseline) {
    //INFO: not supported in all browsers
    var mapping = {
      alphabetic: 'alphabetic',
      hanging: 'hanging',
      top: 'text-before-edge',
      bottom: 'text-after-edge',
      middle: 'central'
    };
    return mapping[textBaseline] || mapping.alphabetic;
  }

  // Unpack entities lookup where the numbers are in radix 32 to reduce the size
  // entity mapping courtesy of tinymce
  namedEntities = createNamedToNumberedLookup(
    '50,nbsp,51,iexcl,52,cent,53,pound,54,curren,55,yen,56,brvbar,57,sect,58,uml,59,copy,' +
      '5a,ordf,5b,laquo,5c,not,5d,shy,5e,reg,5f,macr,5g,deg,5h,plusmn,5i,sup2,5j,sup3,5k,acute,' +
      '5l,micro,5m,para,5n,middot,5o,cedil,5p,sup1,5q,ordm,5r,raquo,5s,frac14,5t,frac12,5u,frac34,' +
      '5v,iquest,60,Agrave,61,Aacute,62,Acirc,63,Atilde,64,Auml,65,Aring,66,AElig,67,Ccedil,' +
      '68,Egrave,69,Eacute,6a,Ecirc,6b,Euml,6c,Igrave,6d,Iacute,6e,Icirc,6f,Iuml,6g,ETH,6h,Ntilde,' +
      '6i,Ograve,6j,Oacute,6k,Ocirc,6l,Otilde,6m,Ouml,6n,times,6o,Oslash,6p,Ugrave,6q,Uacute,' +
      '6r,Ucirc,6s,Uuml,6t,Yacute,6u,THORN,6v,szlig,70,agrave,71,aacute,72,acirc,73,atilde,74,auml,' +
      '75,aring,76,aelig,77,ccedil,78,egrave,79,eacute,7a,ecirc,7b,euml,7c,igrave,7d,iacute,7e,icirc,' +
      '7f,iuml,7g,eth,7h,ntilde,7i,ograve,7j,oacute,7k,ocirc,7l,otilde,7m,ouml,7n,divide,7o,oslash,' +
      '7p,ugrave,7q,uacute,7r,ucirc,7s,uuml,7t,yacute,7u,thorn,7v,yuml,ci,fnof,sh,Alpha,si,Beta,' +
      'sj,Gamma,sk,Delta,sl,Epsilon,sm,Zeta,sn,Eta,so,Theta,sp,Iota,sq,Kappa,sr,Lambda,ss,Mu,' +
      'st,Nu,su,Xi,sv,Omicron,t0,Pi,t1,Rho,t3,Sigma,t4,Tau,t5,Upsilon,t6,Phi,t7,Chi,t8,Psi,' +
      't9,Omega,th,alpha,ti,beta,tj,gamma,tk,delta,tl,epsilon,tm,zeta,tn,eta,to,theta,tp,iota,' +
      'tq,kappa,tr,lambda,ts,mu,tt,nu,tu,xi,tv,omicron,u0,pi,u1,rho,u2,sigmaf,u3,sigma,u4,tau,' +
      'u5,upsilon,u6,phi,u7,chi,u8,psi,u9,omega,uh,thetasym,ui,upsih,um,piv,812,bull,816,hellip,' +
      '81i,prime,81j,Prime,81u,oline,824,frasl,88o,weierp,88h,image,88s,real,892,trade,89l,alefsym,' +
      '8cg,larr,8ch,uarr,8ci,rarr,8cj,darr,8ck,harr,8dl,crarr,8eg,lArr,8eh,uArr,8ei,rArr,8ej,dArr,' +
      '8ek,hArr,8g0,forall,8g2,part,8g3,exist,8g5,empty,8g7,nabla,8g8,isin,8g9,notin,8gb,ni,8gf,prod,' +
      '8gh,sum,8gi,minus,8gn,lowast,8gq,radic,8gt,prop,8gu,infin,8h0,ang,8h7,and,8h8,or,8h9,cap,8ha,cup,' +
      '8hb,int,8hk,there4,8hs,sim,8i5,cong,8i8,asymp,8j0,ne,8j1,equiv,8j4,le,8j5,ge,8k2,sub,8k3,sup,8k4,' +
      'nsub,8k6,sube,8k7,supe,8kl,oplus,8kn,otimes,8l5,perp,8m5,sdot,8o8,lceil,8o9,rceil,8oa,lfloor,8ob,' +
      'rfloor,8p9,lang,8pa,rang,9ea,loz,9j0,spades,9j3,clubs,9j5,hearts,9j6,diams,ai,OElig,aj,oelig,b0,' +
      'Scaron,b1,scaron,bo,Yuml,m6,circ,ms,tilde,802,ensp,803,emsp,809,thinsp,80c,zwnj,80d,zwj,80e,lrm,' +
      '80f,rlm,80j,ndash,80k,mdash,80o,lsquo,80p,rsquo,80q,sbquo,80s,ldquo,80t,rdquo,80u,bdquo,810,dagger,' +
      '811,Dagger,81g,permil,81p,lsaquo,81q,rsaquo,85c,euro',
    32
  );

  //Some basic mappings for attributes and default values.
  STYLES = {
    strokeStyle: {
      svgAttr: 'stroke', //corresponding svg attribute
      canvas: '#000000', //canvas default
      svg: 'none', //svg default
      apply: 'stroke' //apply on stroke() or fill()
    },
    fillStyle: {
      svgAttr: 'fill',
      canvas: '#000000',
      svg: null, //svg default is black, but we need to special case this to handle canvas stroke without fill
      apply: 'fill'
    },
    lineCap: {
      svgAttr: 'stroke-linecap',
      canvas: 'butt',
      svg: 'butt',
      apply: 'stroke'
    },
    lineJoin: {
      svgAttr: 'stroke-linejoin',
      canvas: 'miter',
      svg: 'miter',
      apply: 'stroke'
    },
    miterLimit: {
      svgAttr: 'stroke-miterlimit',
      canvas: 10,
      svg: 4,
      apply: 'stroke'
    },
    lineWidth: {
      svgAttr: 'stroke-width',
      canvas: 1,
      svg: 1,
      apply: 'stroke'
    },
    globalAlpha: {
      svgAttr: 'opacity',
      canvas: 1,
      svg: 1,
      apply: 'fill stroke'
    },
    font: {
      //font converts to multiple svg attributes, there is custom logic for this
      canvas: '12px Arial'
    },
    shadowColor: {
      canvas: '#000000'
    },
    shadowOffsetX: {
      canvas: 0
    },
    shadowOffsetY: {
      canvas: 0
    },
    shadowBlur: {
      canvas: 0
    },
    textAlign: {
      canvas: 'start'
    },
    textBaseline: {
      canvas: 'alphabetic'
    },
    lineDash: {
      svgAttr: 'stroke-dasharray',
      canvas: [],
      svg: null,
      apply: 'stroke'
    }
  };

  /**
   *
   * @param gradientNode - reference to the gradient
   * @constructor
   */
  CanvasGradient = function(gradientNode, ctx) {
    this.__root = gradientNode;
    this.__ctx = ctx;
  };

  /**
   * Adds a color stop to the gradient root
   */
  CanvasGradient.prototype.addColorStop = function(offset, color) {
    var stop = this.__ctx.__createElement('stop'),
      regex,
      matches;
    stop.setAttribute('offset', offset);
    if (color.indexOf('rgba') !== -1) {
      //separate alpha value, since webkit can't handle it
      regex = /rgba\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d?\.?\d*)\s*\)/gi;
      matches = regex.exec(color);
      stop.setAttribute(
        'stop-color',
        format('rgb({r},{g},{b})', {
          r: matches[1],
          g: matches[2],
          b: matches[3]
        })
      );
      stop.setAttribute('stop-opacity', matches[4]);
    } else {
      stop.setAttribute('stop-color', color);
    }
    this.__root.appendChild(stop);
  };

  CanvasPattern = function(pattern, ctx) {
    this.__root = pattern;
    this.__ctx = ctx;
  };

  /**
   * The mock canvas context
   * @param o - options include:
   * ctx - existing Context2D to wrap around
   * width - width of your canvas (defaults to 500)
   * height - height of your canvas (defaults to 500)
   * enableMirroring - enables canvas mirroring (get image data) (defaults to false)
   * document - the document object (defaults to the current document)
   */
  ctx = function(o) {
    var defaultOptions = { width: 500, height: 500, enableMirroring: false },
      options;

    //keep support for this way of calling C2S: new C2S(width,height)
    if (arguments.length > 1) {
      options = defaultOptions;
      options.width = arguments[0];
      options.height = arguments[1];
    } else if (!o) {
      options = defaultOptions;
    } else {
      options = o;
    }

    if (!(this instanceof ctx)) {
      //did someone call this without new?
      return new ctx(options);
    }

    //setup options
    this.width = options.width || defaultOptions.width;
    this.height = options.height || defaultOptions.height;
    this.enableMirroring =
      options.enableMirroring !== undefined
        ? options.enableMirroring
        : defaultOptions.enableMirroring;

    this.canvas = this; ///point back to this instance!
    this.__document = options.document || document;

    // allow passing in an existing context to wrap around
    // if a context is passed in, we know a canvas already exist
    if (options.ctx) {
      this.__ctx = options.ctx;
    } else {
      this.__canvas = this.__document.createElement('canvas');
      this.__ctx = this.__canvas.getContext('2d');
    }

    this.__setDefaultStyles();
    this.__stack = [this.__getStyleState()];
    this.__groupStack = [];

    //the root svg element
    this.__root = this.__document.createElementNS(
      'http://www.w3.org/2000/svg',
      'svg'
    );
    this.__root.setAttribute('version', 1.1);
    this.__root.setAttribute('xmlns', 'http://www.w3.org/2000/svg');
    this.__root.setAttributeNS(
      'http://www.w3.org/2000/xmlns/',
      'xmlns:xlink',
      'http://www.w3.org/1999/xlink'
    );
    this.__root.setAttribute('width', this.width);
    this.__root.setAttribute('height', this.height);

    //make sure we don't generate the same ids in defs
    this.__ids = {};

    //defs tag
    this.__defs = this.__document.createElementNS(
      'http://www.w3.org/2000/svg',
      'defs'
    );
    this.__root.appendChild(this.__defs);

    //also add a group child. the svg element can't use the transform attribute
    this.__currentElement = this.__document.createElementNS(
      'http://www.w3.org/2000/svg',
      'g'
    );
    this.__root.appendChild(this.__currentElement);
  };

  /**
   * Creates the specified svg element
   * @private
   */
  ctx.prototype.__createElement = function(elementName, properties, resetFill) {
    if (typeof properties === 'undefined') {
      properties = {};
    }

    var element = this.__document.createElementNS(
        'http://www.w3.org/2000/svg',
        elementName
      ),
      keys = Object.keys(properties),
      i,
      key;
    if (resetFill) {
      //if fill or stroke is not specified, the svg element should not display. By default SVG's fill is black.
      element.setAttribute('fill', 'none');
      element.setAttribute('stroke', 'none');
    }
    for (i = 0; i < keys.length; i++) {
      key = keys[i];
      element.setAttribute(key, properties[key]);
    }
    return element;
  };

  /**
   * Applies default canvas styles to the context
   * @private
   */
  ctx.prototype.__setDefaultStyles = function() {
    //default 2d canvas context properties see:http://www.w3.org/TR/2dcontext/
    var keys = Object.keys(STYLES),
      i,
      key;
    for (i = 0; i < keys.length; i++) {
      key = keys[i];
      this[key] = STYLES[key].canvas;
    }
  };

  ctx.prototype.setAttrs = function(pen) {
    if (!pen) {
      return;
    }

    var currentElement = this.__currentElement;
    currentElement.setAttribute('id', pen.id);
    currentElement.setAttribute('name', pen.name);
    pen.text && currentElement.setAttribute('text', pen.text);
    pen.lineName && currentElement.setAttribute('line-name', pen.lineName);
    // 连线起终点
    if (pen.type == 1) {
      const from = pen.anchors[0];
      from.connectTo && currentElement.setAttribute('from-id', from.connectTo);
      const to = pen.anchors[pen.anchors.length - 1];
      to.connectTo && currentElement.setAttribute('to-id', to.connectTo);
    }

    // 业务数据
    if (!Array.isArray(pen.form)) {
      return;
    }
    pen.form.forEach(({key}) => {
      // TODO: pen[key] 若是一个对象，待考虑
      currentElement.setAttribute('data-' + key, pen[key]);
    });
  };

  /**
   * Applies styles on restore
   * @param styleState
   * @private
   */
  ctx.prototype.__applyStyleState = function(styleState) {
    var keys = Object.keys(styleState),
      i,
      key;
    for (i = 0; i < keys.length; i++) {
      key = keys[i];
      this[key] = styleState[key];
    }
  };

  /**
   * Gets the current style state
   * @return {Object}
   * @private
   */
  ctx.prototype.__getStyleState = function() {
    var i,
      styleState = {},
      keys = Object.keys(STYLES),
      key;
    for (i = 0; i < keys.length; i++) {
      key = keys[i];
      styleState[key] = this[key];
    }
    return styleState;
  };

  /**
   * Apples the current styles to the current SVG element. On "ctx.fill" or "ctx.stroke"
   * @param type
   * @private
   */
  ctx.prototype.__applyStyleToCurrentElement = function(type) {
    var currentElement = this.__currentElement;
    var currentStyleGroup = this.__currentElementsToStyle;
    if (currentStyleGroup) {
      currentElement.setAttribute(type, '');
      currentElement = currentStyleGroup.element;
      currentStyleGroup.children.forEach(function(node) {
        node.setAttribute(type, '');
      });
    }

    var keys = Object.keys(STYLES),
      i,
      style,
      value,
      id,
      regex,
      matches;
    for (i = 0; i < keys.length; i++) {
      style = STYLES[keys[i]];
      value = this[keys[i]];
      if (style.apply) {
        //is this a gradient or pattern?
        if (value instanceof CanvasPattern) {
          //pattern
          if (value.__ctx) {
            //copy over defs
            while (value.__ctx.__defs.childNodes.length) {
              id = value.__ctx.__defs.childNodes[0].getAttribute('id');
              this.__ids[id] = id;
              this.__defs.appendChild(value.__ctx.__defs.childNodes[0]);
            }
          }
          currentElement.setAttribute(
            style.apply,
            format('url(#{id})', { id: value.__root.getAttribute('id') })
          );
        } else if (value instanceof CanvasGradient) {
          //gradient
          currentElement.setAttribute(
            style.apply,
            format('url(#{id})', { id: value.__root.getAttribute('id') })
          );
        } else if (style.apply.indexOf(type) !== -1 && style.svg !== value) {
          if (
            (style.svgAttr === 'stroke' || style.svgAttr === 'fill') &&
            value &&
            value.indexOf('rgba') !== -1
          ) {
            //separate alpha value, since illustrator can't handle it
            regex = /rgba\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d?\.?\d*)\s*\)/gi;
            matches = regex.exec(value);
            currentElement.setAttribute(
              style.svgAttr,
              format('rgb({r},{g},{b})', {
                r: matches[1],
                g: matches[2],
                b: matches[3]
              })
            );
            //should take globalAlpha here
            var opacity = matches[4];
            var globalAlpha = this.globalAlpha;
            if (globalAlpha != null) {
              opacity *= globalAlpha;
            }
            currentElement.setAttribute(style.svgAttr + '-opacity', opacity);
          } else {
            var attr = style.svgAttr;
            if (keys[i] === 'globalAlpha') {
              attr = type + '-' + style.svgAttr;
              if (currentElement.getAttribute(attr)) {
                //fill-opacity or stroke-opacity has already been set by stroke or fill.
                continue;
              }
            }
            //otherwise only update attribute if right type, and not svg default
            currentElement.setAttribute(attr, value);
          }
        }
      }
    }
  };

  /**
   * Will return the closest group or svg node. May return the current element.
   * @private
   */
  ctx.prototype.__closestGroupOrSvg = function(node) {
    node = node || this.__currentElement;
    if (node.nodeName === 'g' || node.nodeName === 'svg') {
      return node;
    } else {
      return this.__closestGroupOrSvg(node.parentNode);
    }
  };

  /**
   * Returns the serialized value of the svg so far
   * @param fixNamedEntities - Standalone SVG doesn't support named entities, which document.createTextNode encodes.
   *                           If true, we attempt to find all named entities and encode it as a numeric entity.
   * @return serialized svg
   */
  ctx.prototype.getSerializedSvg = function(fixNamedEntities) {
    var serialized = new XMLSerializer().serializeToString(this.__root),
      keys,
      i,
      key,
      value,
      regexp,
      xmlns;

    //IE search for a duplicate xmnls because they didn't implement setAttributeNS correctly
    xmlns = /xmlns="http:\/\/www\.w3\.org\/2000\/svg".+xmlns="http:\/\/www\.w3\.org\/2000\/svg/gi;
    if (xmlns.test(serialized)) {
      serialized = serialized.replace(
        'xmlns="http://www.w3.org/2000/svg',
        'xmlns:xlink="http://www.w3.org/1999/xlink'
      );
    }

    if (fixNamedEntities) {
      keys = Object.keys(namedEntities);
      //loop over each named entity and replace with the proper equivalent.
      for (i = 0; i < keys.length; i++) {
        key = keys[i];
        value = namedEntities[key];
        regexp = new RegExp(key, 'gi');
        if (regexp.test(serialized)) {
          serialized = serialized.replace(regexp, value);
        }
      }
    }

    return serialized;
  };

  /**
   * Returns the root svg
   * @return
   */
  ctx.prototype.getSvg = function() {
    return this.__root;
  };
  /**
   * Will generate a group tag.
   */
  ctx.prototype.save = function() {
    var group = this.__createElement('g');
    var parent = this.__closestGroupOrSvg();
    this.__groupStack.push(parent);
    parent.appendChild(group);
    this.__currentElement = group;
    this.__stack.push(this.__getStyleState());
  };
  /**
   * Sets current element to parent, or just root if already root
   */
  ctx.prototype.restore = function() {
    this.__currentElement = this.__groupStack.pop();
    this.__currentElementsToStyle = null;
    //Clearing canvas will make the poped group invalid, currentElement is set to the root group node.
    if (!this.__currentElement) {
      this.__currentElement = this.__root.childNodes[1];
    }
    var state = this.__stack.pop();
    this.__applyStyleState(state);
  };

  /**
   * Helper method to add transform
   * @private
   */
  ctx.prototype.__addTransform = function(t) {
    //if the current element has siblings, add another group
    var parent = this.__closestGroupOrSvg();
    if (parent.childNodes.length > 0) {
      if (this.__currentElement.nodeName === 'path') {
        if (!this.__currentElementsToStyle)
          this.__currentElementsToStyle = { element: parent, children: [] };
        this.__currentElementsToStyle.children.push(this.__currentElement);
        this.__applyCurrentDefaultPath();
      }

      var group = this.__createElement('g');
      parent.appendChild(group);
      this.__currentElement = group;
    }

    var transform = this.__currentElement.getAttribute('transform');
    if (transform) {
      transform += ' ';
    } else {
      transform = '';
    }
    transform += t;
    this.__currentElement.setAttribute('transform', transform);
  };

  /**
   *  scales the current element
   */
  ctx.prototype.scale = function(x, y) {
    if (y === undefined) {
      y = x;
    }
    this.__addTransform(format('scale({x},{y})', { x: x, y: y }));
  };

  /**
   * rotates the current element
   */
  ctx.prototype.rotate = function(angle) {
    var degrees = (angle * 180) / Math.PI;
    this.__addTransform(
      format('rotate({angle},{cx},{cy})', { angle: degrees, cx: 0, cy: 0 })
    );
  };

  /**
   * translates the current element
   */
  ctx.prototype.translate = function(x, y) {
    this.__addTransform(format('translate({x},{y})', { x: x, y: y }));
  };

  /**
   * applies a transform to the current element
   */
  ctx.prototype.transform = function(a, b, c, d, e, f) {
    this.__addTransform(
      format('matrix({a},{b},{c},{d},{e},{f})', {
        a: a,
        b: b,
        c: c,
        d: d,
        e: e,
        f: f
      })
    );
  };

  /**
   * Create a new Path Element
   */
  ctx.prototype.beginPath = function() {
    var path, parent;

    // Note that there is only one current default path, it is not part of the drawing state.
    // See also: https://html.spec.whatwg.org/multipage/scripting.html#current-default-path
    this.__currentDefaultPath = '';
    this.__currentPosition = {};

    path = this.__createElement('path', {}, true);
    parent = this.__closestGroupOrSvg();
    parent.appendChild(path);
    this.__currentElement = path;
  };

  /**
   * Helper function to apply currentDefaultPath to current path element
   * @private
   */
  ctx.prototype.__applyCurrentDefaultPath = function() {
    var currentElement = this.__currentElement;
    if (currentElement.nodeName === 'path') {
      currentElement.setAttribute('d', this.__currentDefaultPath);
    } else {
      console.error(
        'Attempted to apply path command to node',
        currentElement.nodeName
      );
    }
  };

  ctx.prototype.svgPath = function(text) {
    this.__addPathCommand(text);
  };

  /**
   * Helper function to add path command
   * @private
   */
  ctx.prototype.__addPathCommand = function(command) {
    this.__currentDefaultPath += ' ';
    this.__currentDefaultPath += command;
  };

  /**
   * Adds the move command to the current path element,
   * if the currentPathElement is not empty create a new path element
   */
  ctx.prototype.moveTo = function(x, y) {
    if (this.__currentElement.nodeName !== 'path') {
      this.beginPath();
    }

    // creates a new subpath with the given point
    this.__currentPosition = { x: x, y: y };
    this.__addPathCommand(format('M {x} {y}', { x: x, y: y }));
  };

  /**
   * Closes the current path
   */
  ctx.prototype.closePath = function() {
    if (this.__currentDefaultPath) {
      this.__addPathCommand('Z');
    }
  };

  /**
   * Adds a line to command
   */
  ctx.prototype.lineTo = function(x, y) {
    this.__currentPosition = { x: x, y: y };
    if (this.__currentDefaultPath.indexOf('M') > -1) {
      this.__addPathCommand(format('L {x} {y}', { x: x, y: y }));
    } else {
      this.__addPathCommand(format('M {x} {y}', { x: x, y: y }));
    }
  };

  /**
   * Add a bezier command
   */
  ctx.prototype.bezierCurveTo = function(cp1x, cp1y, cp2x, cp2y, x, y) {
    this.__currentPosition = { x: x, y: y };
    this.__addPathCommand(
      format('C {cp1x} {cp1y} {cp2x} {cp2y} {x} {y}', {
        cp1x: cp1x,
        cp1y: cp1y,
        cp2x: cp2x,
        cp2y: cp2y,
        x: x,
        y: y
      })
    );
  };

  /**
   * Adds a quadratic curve to command
   */
  ctx.prototype.quadraticCurveTo = function(cpx, cpy, x, y) {
    this.__currentPosition = { x: x, y: y };
    this.__addPathCommand(
      format('Q {cpx} {cpy} {x} {y}', { cpx: cpx, cpy: cpy, x: x, y: y })
    );
  };

  /**
   * Return a new normalized vector of given vector
   */
  var normalize = function(vector) {
    var len = Math.sqrt(vector[0] * vector[0] + vector[1] * vector[1]);
    return [vector[0] / len, vector[1] / len];
  };

  /**
   * Adds the arcTo to the current path
   *
   * @see http://www.w3.org/TR/2015/WD-2dcontext-20150514/#dom-context-2d-arcto
   */
  ctx.prototype.arcTo = function(x1, y1, x2, y2, radius) {
    // Let the point (x0, y0) be the last point in the subpath.
    var x0 = this.__currentPosition && this.__currentPosition.x;
    var y0 = this.__currentPosition && this.__currentPosition.y;

    // First ensure there is a subpath for (x1, y1).
    if (typeof x0 == 'undefined' || typeof y0 == 'undefined') {
      return;
    }

    // Negative values for radius must cause the implementation to throw an IndexSizeError exception.
    if (radius < 0) {
      throw new Error(
        'IndexSizeError: The radius provided (' + radius + ') is negative.'
      );
    }

    // If the point (x0, y0) is equal to the point (x1, y1),
    // or if the point (x1, y1) is equal to the point (x2, y2),
    // or if the radius radius is zero,
    // then the method must add the point (x1, y1) to the subpath,
    // and connect that point to the previous point (x0, y0) by a straight line.
    if ((x0 === x1 && y0 === y1) || (x1 === x2 && y1 === y2) || radius === 0) {
      this.lineTo(x1, y1);
      return;
    }

    // Otherwise, if the points (x0, y0), (x1, y1), and (x2, y2) all lie on a single straight line,
    // then the method must add the point (x1, y1) to the subpath,
    // and connect that point to the previous point (x0, y0) by a straight line.
    var unit_vec_p1_p0 = normalize([x0 - x1, y0 - y1]);
    var unit_vec_p1_p2 = normalize([x2 - x1, y2 - y1]);
    if (
      unit_vec_p1_p0[0] * unit_vec_p1_p2[1] ===
      unit_vec_p1_p0[1] * unit_vec_p1_p2[0]
    ) {
      this.lineTo(x1, y1);
      return;
    }

    // Otherwise, let The Arc be the shortest arc given by circumference of the circle that has radius radius,
    // and that has one point tangent to the half-infinite line that crosses the point (x0, y0) and ends at the point (x1, y1),
    // and that has a different point tangent to the half-infinite line that ends at the point (x1, y1), and crosses the point (x2, y2).
    // The points at which this circle touches these two lines are called the start and end tangent points respectively.

    // note that both vectors are unit vectors, so the length is 1
    var cos =
      unit_vec_p1_p0[0] * unit_vec_p1_p2[0] +
      unit_vec_p1_p0[1] * unit_vec_p1_p2[1];
    var theta = Math.acos(Math.abs(cos));

    // Calculate origin
    var unit_vec_p1_origin = normalize([
      unit_vec_p1_p0[0] + unit_vec_p1_p2[0],
      unit_vec_p1_p0[1] + unit_vec_p1_p2[1]
    ]);
    var len_p1_origin = radius / Math.sin(theta / 2);
    var x = x1 + len_p1_origin * unit_vec_p1_origin[0];
    var y = y1 + len_p1_origin * unit_vec_p1_origin[1];

    // Calculate start angle and end angle
    // rotate 90deg clockwise (note that y axis points to its down)
    var unit_vec_origin_start_tangent = [-unit_vec_p1_p0[1], unit_vec_p1_p0[0]];
    // rotate 90deg counter clockwise (note that y axis points to its down)
    var unit_vec_origin_end_tangent = [unit_vec_p1_p2[1], -unit_vec_p1_p2[0]];
    var getAngle = function(vector) {
      // get angle (clockwise) between vector and (1, 0)
      var x = vector[0];
      var y = vector[1];
      if (y >= 0) {
        // note that y axis points to its down
        return Math.acos(x);
      } else {
        return -Math.acos(x);
      }
    };
    var startAngle = getAngle(unit_vec_origin_start_tangent);
    var endAngle = getAngle(unit_vec_origin_end_tangent);

    // Connect the point (x0, y0) to the start tangent point by a straight line
    this.lineTo(
      x + unit_vec_origin_start_tangent[0] * radius,
      y + unit_vec_origin_start_tangent[1] * radius
    );

    // Connect the start tangent point to the end tangent point by arc
    // and adding the end tangent point to the subpath.
    this.arc(x, y, radius, startAngle, endAngle);
  };

  /**
   * Sets the stroke property on the current element
   */
  ctx.prototype.stroke = function() {
    if (this.__currentElement.nodeName === 'path') {
      this.__currentElement.setAttribute('paint-order', 'fill stroke markers');
    }
    this.__applyCurrentDefaultPath();
    this.__applyStyleToCurrentElement('stroke');
  };

  /**
   * Sets fill properties on the current element
   */
  ctx.prototype.fill = function() {
    if (this.__currentElement.nodeName === 'path') {
      this.__currentElement.setAttribute('paint-order', 'stroke fill markers');
    }
    this.__applyCurrentDefaultPath();
    this.__applyStyleToCurrentElement('fill');
  };

  /**
   *  Adds a rectangle to the path.
   */
  ctx.prototype.rect = function(x, y, width, height) {
    if (this.__currentElement.nodeName !== 'path') {
      this.beginPath();
    }
    this.moveTo(x, y);
    this.lineTo(x + width, y);
    this.lineTo(x + width, y + height);
    this.lineTo(x, y + height);
    this.lineTo(x, y);
    this.closePath();
  };

  /**
   * adds a rectangle element
   */
  ctx.prototype.fillRect = function(x, y, width, height) {
    var rect, parent;
    rect = this.__createElement(
      'rect',
      {
        x: x,
        y: y,
        width: width,
        height: height
      },
      true
    );
    parent = this.__closestGroupOrSvg();
    parent.appendChild(rect);
    this.__currentElement = rect;
    this.__applyStyleToCurrentElement('fill');
  };

  /**
   * Draws a rectangle with no fill
   * @param x
   * @param y
   * @param width
   * @param height
   */
  ctx.prototype.strokeRect = function(x, y, width, height) {
    var rect, parent;
    rect = this.__createElement(
      'rect',
      {
        x: x,
        y: y,
        width: width,
        height: height
      },
      true
    );
    parent = this.__closestGroupOrSvg();
    parent.appendChild(rect);
    this.__currentElement = rect;
    this.__applyStyleToCurrentElement('stroke');
  };

  /**
   * Clear entire canvas:
   * 1. save current transforms
   * 2. remove all the childNodes of the root g element
   */
  ctx.prototype.__clearCanvas = function() {
    var current = this.__closestGroupOrSvg(),
      transform = current.getAttribute('transform');
    var rootGroup = this.__root.childNodes[1];
    var childNodes = rootGroup.childNodes;
    for (var i = childNodes.length - 1; i >= 0; i--) {
      if (childNodes[i]) {
        rootGroup.removeChild(childNodes[i]);
      }
    }
    this.__currentElement = rootGroup;
    //reset __groupStack as all the child group nodes are all removed.
    this.__groupStack = [];
    if (transform) {
      this.__addTransform(transform);
    }
  };

  /**
   * "Clears" a canvas by just drawing a white rectangle in the current group.
   */
  ctx.prototype.clearRect = function(x, y, width, height) {
    //clear entire canvas
    if (x === 0 && y === 0 && width === this.width && height === this.height) {
      this.__clearCanvas();
      return;
    }
    var rect,
      parent = this.__closestGroupOrSvg();
    rect = this.__createElement(
      'rect',
      {
        x: x,
        y: y,
        width: width,
        height: height,
        fill: '#FFFFFF'
      },
      true
    );
    parent.appendChild(rect);
  };

  /**
   * Adds a linear gradient to a defs tag.
   * Returns a canvas gradient object that has a reference to it's parent def
   */
  ctx.prototype.createLinearGradient = function(x1, y1, x2, y2) {
    var grad = this.__createElement(
      'linearGradient',
      {
        id: randomString(this.__ids),
        x1: x1 + 'px',
        x2: x2 + 'px',
        y1: y1 + 'px',
        y2: y2 + 'px',
        gradientUnits: 'userSpaceOnUse'
      },
      false
    );
    this.__defs.appendChild(grad);
    return new CanvasGradient(grad, this);
  };

  /**
   * Adds a radial gradient to a defs tag.
   * Returns a canvas gradient object that has a reference to it's parent def
   */
  ctx.prototype.createRadialGradient = function(x0, y0, r0, x1, y1, r1) {
    var grad = this.__createElement(
      'radialGradient',
      {
        id: randomString(this.__ids),
        cx: x1 + 'px',
        cy: y1 + 'px',
        r: r1 + 'px',
        fx: x0 + 'px',
        fy: y0 + 'px',
        gradientUnits: 'userSpaceOnUse'
      },
      false
    );
    this.__defs.appendChild(grad);
    return new CanvasGradient(grad, this);
  };

  /**
   * Parses the font string and returns svg mapping
   * @private
   */
  ctx.prototype.__parseFont = function() {
    var fontPart = this.font.split(' ') || [];
    if (fontPart[3] && fontPart[3].indexOf('/') > -1) {
      fontPart[3] = fontPart[3].split('/')[0];
    }
    var family = '';
    for (var i = 4; i < fontPart.length; ++i) {
      family += fontPart[i] + ' ';
    }

    if (fontPart.length === 2) {
      family = fontPart[1];
      fontPart = ['normal', 'normal', 'normal', fontPart[0]];
    }

    var data = {
      style: fontPart[0] || 'normal',
      size: fontPart[3] || '12px',
      family: family || 'Arial',
      weight: fontPart[2] || 'normal',
      decoration: fontPart[1] || 'normal',
      href: null
    };

    //canvas doesn't support underline natively, but we can pass this attribute
    if (this.__fontUnderline === 'underline') {
      data.decoration = 'underline';
    }

    //canvas also doesn't support linking, but we can pass this as well
    if (this.__fontHref) {
      data.href = this.__fontHref;
    }

    return data;
  };

  /**
   * Helper to link text fragments
   * @param font
   * @param element
   * @return {*}
   * @private
   */
  ctx.prototype.__wrapTextLink = function(font, element) {
    if (font.href) {
      var a = this.__createElement('a');
      a.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href', font.href);
      a.appendChild(element);
      return a;
    }
    return element;
  };

  /**
   * Fills or strokes text
   * @param text
   * @param x
   * @param y
   * @param action - stroke or fill
   * @private
   */
  ctx.prototype.__applyText = function(text, x, y, action) {
    var font = this.__parseFont(),
      parent = this.__closestGroupOrSvg(),
      textElement = this.__createElement(
        'text',
        {
          'font-family': font.family,
          'font-size': font.size,
          'font-style': font.style,
          'font-weight': font.weight,
          'text-decoration': font.decoration,
          x: x,
          y: y,
          'text-anchor': getTextAnchor(this.textAlign),
          'dominant-baseline': getDominantBaseline(this.textBaseline)
        },
        true
      );

    if (font.family === 'topology') {
      text = '--le5le--' + (+text.charCodeAt()).toString(16) + ';';
    }
    textElement.appendChild(this.__document.createTextNode(text));
    this.__currentElement = textElement;
    this.__applyStyleToCurrentElement(action);
    parent.appendChild(this.__wrapTextLink(font, textElement));
  };

  /**
   * Creates a text element
   * @param text
   * @param x
   * @param y
   */
  ctx.prototype.fillText = function(text, x, y) {
    this.__applyText(text, x, y, 'fill');
  };

  /**
   * Strokes text
   * @param text
   * @param x
   * @param y
   */
  ctx.prototype.strokeText = function(text, x, y) {
    this.__applyText(text, x, y, 'stroke');
  };

  /**
   * No need to implement this for svg.
   * @param text
   * @return {TextMetrics}
   */
  ctx.prototype.measureText = function(text) {
    this.__ctx.font = this.font;
    return this.__ctx.measureText(text);
  };

  /**
   *  Arc command!
   */
  ctx.prototype.arc = function(
    x,
    y,
    radius,
    startAngle,
    endAngle,
    counterClockwise
  ) {
    // in canvas no circle is drawn if no angle is provided.
    if (startAngle === endAngle) {
      return;
    }

    if (this.__currentElement.nodeName !== 'path') {
      this.beginPath();
    }

    startAngle = startAngle % (2 * Math.PI);
    endAngle = endAngle % (2 * Math.PI);
    if (startAngle === endAngle) {
      //circle time! subtract some of the angle so svg is happy (svg elliptical arc can't draw a full circle)
      endAngle =
        (endAngle + 2 * Math.PI - 0.001 * (counterClockwise ? -1 : 1)) %
        (2 * Math.PI);
    }
    var endX = x + radius * Math.cos(endAngle),
      endY = y + radius * Math.sin(endAngle),
      startX = x + radius * Math.cos(startAngle),
      startY = y + radius * Math.sin(startAngle),
      sweepFlag = counterClockwise ? 0 : 1,
      largeArcFlag = 0,
      diff = endAngle - startAngle;

    // https://github.com/gliffy/canvas2svg/issues/4
    if (diff < 0) {
      diff += 2 * Math.PI;
    }

    if (counterClockwise) {
      largeArcFlag = diff > Math.PI ? 0 : 1;
    } else {
      largeArcFlag = diff > Math.PI ? 1 : 0;
    }

    this.lineTo(startX, startY);
    this.__addPathCommand(
      format(
        'A {rx} {ry} {xAxisRotation} {largeArcFlag} {sweepFlag} {endX} {endY}',
        {
          rx: radius,
          ry: radius,
          xAxisRotation: 0,
          largeArcFlag: largeArcFlag,
          sweepFlag: sweepFlag,
          endX: endX,
          endY: endY
        }
      )
    );

    this.__currentPosition = { x: endX, y: endY };
  };

  /**
   * Generates a ClipPath from the clip command.
   */
  ctx.prototype.clip = function() {
    var group = this.__closestGroupOrSvg(),
      clipPath = this.__createElement('clipPath'),
      id = randomString(this.__ids),
      newGroup = this.__createElement('g');

    this.__applyCurrentDefaultPath();
    group.removeChild(this.__currentElement);
    clipPath.setAttribute('id', id);
    clipPath.appendChild(this.__currentElement);

    this.__defs.appendChild(clipPath);

    //set the clip path to this group
    group.setAttribute('clip-path', format('url(#{id})', { id: id }));

    //clip paths can be scaled and transformed, we need to add another wrapper group to avoid later transformations
    // to this path
    group.appendChild(newGroup);

    this.__currentElement = newGroup;
  };

  /**
   * Draws a canvas, image or mock context to this canvas.
   * Note that all svg dom manipulation uses node.childNodes rather than node.children for IE support.
   * http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html#dom-context-2d-drawimage
   */
  ctx.prototype.drawImage = function() {
    //convert arguments to a real array
    var args = Array.prototype.slice.call(arguments),
      image = args[0],
      dx,
      dy,
      dw,
      dh,
      sx = 0,
      sy = 0,
      sw,
      sh,
      parent,
      svg,
      defs,
      group,
      currentElement,
      svgImage,
      canvas,
      context,
      id;

    if (args.length === 3) {
      dx = args[1];
      dy = args[2];
      sw = image.width;
      sh = image.height;
      dw = sw;
      dh = sh;
    } else if (args.length === 5) {
      dx = args[1];
      dy = args[2];
      dw = args[3];
      dh = args[4];
      sw = image.width;
      sh = image.height;
    } else if (args.length === 9) {
      sx = args[1];
      sy = args[2];
      sw = args[3];
      sh = args[4];
      dx = args[5];
      dy = args[6];
      dw = args[7];
      dh = args[8];
    } else {
      throw new Error(
        'Invalid number of arguments passed to drawImage: ' + arguments.length
      );
    }

    parent = this.__closestGroupOrSvg();
    currentElement = this.__currentElement;
    var translateDirective = 'translate(' + dx + ', ' + dy + ')';
    if (image instanceof ctx) {
      //canvas2svg mock canvas context. In the future we may want to clone nodes instead.
      //also I'm currently ignoring dw, dh, sw, sh, sx, sy for a mock context.
      svg = image.getSvg().cloneNode(true);
      if (svg.childNodes && svg.childNodes.length > 1) {
        defs = svg.childNodes[0];
        while (defs.childNodes.length) {
          id = defs.childNodes[0].getAttribute('id');
          this.__ids[id] = id;
          this.__defs.appendChild(defs.childNodes[0]);
        }
        group = svg.childNodes[1];
        if (group) {
          //save original transform
          var originTransform = group.getAttribute('transform');
          var transformDirective;
          if (originTransform) {
            transformDirective = originTransform + ' ' + translateDirective;
          } else {
            transformDirective = translateDirective;
          }
          group.setAttribute('transform', transformDirective);
          parent.appendChild(group);
        }
      }
    } else if (image.nodeName === 'CANVAS' || image.nodeName === 'IMG') {
      //canvas or image
      svgImage = this.__createElement('image');
      svgImage.setAttribute('width', dw);
      svgImage.setAttribute('height', dh);
      svgImage.setAttribute('preserveAspectRatio', 'none');

      if (sx || sy || sw !== image.width || sh !== image.height) {
        //crop the image using a temporary canvas
        canvas = this.__document.createElement('canvas');
        canvas.width = dw;
        canvas.height = dh;
        context = canvas.getContext('2d');
        context.drawImage(image, sx, sy, sw, sh, 0, 0, dw, dh);
        image = canvas;
      }
      svgImage.setAttribute('transform', translateDirective);
      var imgSrc = image.getAttribute('src');
      if (imgSrc[0] === '/') {
        imgSrc = location.protocol + '//' + location.host + imgSrc;
      }
      svgImage.setAttributeNS(
        'http://www.w3.org/1999/xlink',
        'xlink:href',
        image.nodeName === 'CANVAS' ? image.toDataURL() : imgSrc
      );
      parent.appendChild(svgImage);
    }
  };

  /**
   * Generates a pattern tag
   */
  ctx.prototype.createPattern = function(image, repetition) {
    var pattern = this.__document.createElementNS(
        'http://www.w3.org/2000/svg',
        'pattern'
      ),
      id = randomString(this.__ids),
      img;
    pattern.setAttribute('id', id);
    pattern.setAttribute('width', image.width);
    pattern.setAttribute('height', image.height);
    if (image.nodeName === 'CANVAS' || image.nodeName === 'IMG') {
      img = this.__document.createElementNS(
        'http://www.w3.org/2000/svg',
        'image'
      );
      img.setAttribute('width', image.width);
      img.setAttribute('height', image.height);
      img.setAttributeNS(
        'http://www.w3.org/1999/xlink',
        'xlink:href',
        image.nodeName === 'CANVAS'
          ? image.toDataURL()
          : image.getAttribute('src')
      );
      pattern.appendChild(img);
      this.__defs.appendChild(pattern);
    } else if (image instanceof ctx) {
      pattern.appendChild(image.__root.childNodes[1]);
      this.__defs.appendChild(pattern);
    }
    return new CanvasPattern(pattern, this);
  };

  ctx.prototype.setLineDash = function(dashArray) {
    if (dashArray && dashArray.length > 0) {
      this.lineDash = dashArray.join(',');
    } else {
      this.lineDash = null;
    }
  };

  /*
   * Ellipse command
   * @param x
   * @param y
   * @param radiusX
   * @param radiusY
   * @param startAngle
   * @param endAngle
   * @counterClockwise
   */
  ctx.prototype.ellipse = function(
    x,
    y,
    radiusX,
    radiusY,
    rotation,
    startAngle,
    endAngle,
    counterClockwise
  ) {
    //ellipse is the same svg command as arc, but with a radiusX and radiusY instead of just radius
    if (startAngle === endAngle) {
      return;
    }

    if (this.__currentElement.nodeName !== 'path') {
      this.beginPath();
    }

    startAngle = startAngle % (2 * Math.PI);
    endAngle = endAngle % (2 * Math.PI);
    if (startAngle === endAngle) {
      endAngle =
        (endAngle + 2 * Math.PI - 0.001 * (counterClockwise ? -1 : 1)) %
        (2 * Math.PI);
    }
    var endX =
        x +
        Math.cos(-rotation) * radiusX * Math.cos(endAngle) +
        Math.sin(-rotation) * radiusY * Math.sin(endAngle),
      endY =
        y -
        Math.sin(-rotation) * radiusX * Math.cos(endAngle) +
        Math.cos(-rotation) * radiusY * Math.sin(endAngle),
      startX =
        x +
        Math.cos(-rotation) * radiusX * Math.cos(startAngle) +
        Math.sin(-rotation) * radiusY * Math.sin(startAngle),
      startY =
        y -
        Math.sin(-rotation) * radiusX * Math.cos(startAngle) +
        Math.cos(-rotation) * radiusY * Math.sin(startAngle),
      sweepFlag = counterClockwise ? 0 : 1,
      largeArcFlag = 0,
      diff = endAngle - startAngle;

    if (diff < 0) {
      diff += 2 * Math.PI;
    }

    if (counterClockwise) {
      largeArcFlag = diff > Math.PI ? 0 : 1;
    } else {
      largeArcFlag = diff > Math.PI ? 1 : 0;
    }

    this.lineTo(startX, startY);
    this.__addPathCommand(
      format(
        'A {rx} {ry} {xAxisRotation} {largeArcFlag} {sweepFlag} {endX} {endY}',
        {
          rx: radiusX,
          ry: radiusY,
          xAxisRotation: rotation * (180 / Math.PI),
          largeArcFlag: largeArcFlag,
          sweepFlag: sweepFlag,
          endX: endX,
          endY: endY
        }
      )
    );

    this.__currentPosition = { x: endX, y: endY };
  };

  /**
   * Not yet implemented
   */
  ctx.prototype.drawFocusRing = function() {};
  ctx.prototype.createImageData = function() {};
  ctx.prototype.getImageData = function() {};
  ctx.prototype.putImageData = function() {};
  ctx.prototype.globalCompositeOperation = function() {};
  ctx.prototype.setTransform = function() {};

  //add options for alternative namespace
  if (typeof window === 'object') {
    window.C2S = ctx;
  }

  // CommonJS/Browserify
  if (typeof module === 'object' && typeof module.exports === 'object') {
    module.exports = ctx;
  }
})();