HTML5 signature pad to image

In this article, we will create a signature in the signature pad with the help of a mouse.
We can use the combination of HTML5 and JavaScript.
What do you mean by Signature pad?

Signature Pad is a JavaScript library for drawing smooth signatures. It works in all modern desktop and mobile browsers and doesn’t depend on any external libraries.
Let’s take below example of using Signature pad in HTML5
Example:

  <! DOCTYPE html>  <html>  <head>  <title>  Draw Signature with mouse or touch  </title>  <style>     @import url(https://fonts.googleapis.com/css?family=Open+Sans:400,700);  body {        background: #4e54c8;        background: -webkit-linear-gradient(to left, #8f94fb, #4e54c8);        width: 100%;      height:100vh;  }  *,  :before,  :after {    box-sizing: border-box;  }  html {    font: 18px ‘Helvetica Neue’, sans-serif;  }  body {    text-align: center;  }  .signature-component {    text-align: left;    display: inline-block;    max-width: 100%;    }    h1 {      margin-bottom: 0;    }    h2 {      margin: 0;      font-size: 100%;    }    button {      padding: 1em;      background: transparent;      box-shadow: 2px 2px 4px #777;      margin-top: .5em;      border: 1px solid #777;      font-size: 1rem;      &.toggle {        background: rgba(red, .2);      }    }    canvas {      display: block;      position: relative;      border: 1px solid;        }    img {      position: absolute;      left: 0;      top: 0;    }  .circles {      position: absolute;      top: 0;      left: 0;      width: 100%;      height: 100%;      overflow: hidden;  }  .circles li {      position: absolute;      display: block;      list-style: none;      width: 20px;      height: 20px;      background: rgba(255, 255, 255, 0.2);      animation: animate 25s linear infinite;      bottom: -150px;    }  .circles li:nth-child(1) {      left: 25%;      width: 80px;      height: 80px;      animation-delay: 0s;  }  .circles li:nth-child(2) {      left: 10%;      width: 20px;      height: 20px;      animation-delay: 2s;      animation-duration: 12s;  }  .circles li:nth-child(3) {      left: 70%;      width: 20px;      height: 20px;      animation-delay: 4s;  }  .circles li:nth-child(4) {      left: 40%;      width: 60px;      height: 60px;      animation-delay: 0s;      animation-duration: 18s;  }  .circles li:nth-child(5) {      left: 65%;      width: 20px;      height: 20px;      animation-delay: 0s;  }  .circles li:nth-child(6) {      left: 75%;      width: 110px;      height: 110px;      animation-delay: 3s;  }  .circles li:nth-child(7) {      left: 35%;      width: 150px;      height: 150px;      animation-delay: 7s;  }  .circles li:nth-child(8) {      left: 50%;      width: 25px;      height: 25px;      animation-delay: 15s;      animation-duration: 45s;  }  .circles li:nth-child(9) {      left: 20%;      width: 15px;      height: 15px;      animation-delay: 2s;      animation-duration: 35s;  }  .circles li:nth-child(10) {      left: 85%;      width: 150px;      height: 150px;      animation-delay: 0s;      animation-duration: 11s;  }  @keyframes animate {  0% {          transform: translateY(0) rotate(0deg);          opacity: 1;          border-radius: 0;      }      100% {          transform: translateY(-1000px) rotate(720deg);          opacity: 0;          border-radius: 50%;      }  }  </style>  </head>  <body>  <div class=”area” >              <ul class=”circles”>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>                      <li></li>              </ul>      </div >  <section class=”signature-component”>    <h1> Example </h1>    <h2> Draw Signature with mouse or touch </h2>    <canvas id=”signature-pad” width=”400″ height=”200″> </canvas>    <div>      <button id=”clear”> Clear </button>    </div>   </section>  <script src=”https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js”> </script>   <script src=”https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js”> </script>   <script type=”text/javascript”>  $(function () {  var SignaturePad = (function(document) {      “use strict”;      var log = console.log.bind(console);      var SignaturePad = function(canvas, options) {          var self = this,             opts = options || {};          this.velocityFilterWeight = opts.velocityFilterWeight || 0.7;          this.minWidth = opts.minWidth || 0.5;          this.maxWidth = opts.maxWidth || 2.5;          this.dotSize = opts.dotSize || function() {                  return (self.minWidth + self.maxWidth) / 2;              };          this.penColor = opts.penColor || “black”;          this.backgroundColor = opts.backgroundColor || “rgba(0,0,0,0)”;          this.throttle = opts.throttle || 0;          this.throttleOptions = {              leading: true,              trailing: true          };          this.minPointDistance = opts.minPointDistance || 0;          this.onEnd = opts.onEnd;          this.onBegin = opts.onBegin;          this._canvas = canvas;          this._ctx = canvas.getContext(“2d”);          this._ctx.lineCap = ’round’;          this.clear();          this._handleMouseDown = function(event) {              if (event.which === 1) {                  self._mouseButtonDown = true;                  self._strokeBegin(event);              }          };          var _handleMouseMove = function(event) {             event.preventDefault();              if (self._mouseButtonDown) {                  self._strokeUpdate(event);                  if (self.arePointsDisplayed) {                      var point = self._createPoint(event);                      self._drawMark(point.x, point.y, 5);                  }              }          };          this._handleMouseMove = _.throttle(_handleMouseMove, self.throttle, self.throttleOptions);          this._handleMouseUp = function(event) {              if (event.which === 1 && self._mouseButtonDown) {                  self._mouseButtonDown = false;                  self._strokeEnd(event);              }          };          this._handleTouchStart = function(event) {              if (event.targetTouches.length == 1) {                  var touch = event.changedTouches[0];                  self._strokeBegin(touch);              }          };          var _handleTouchMove = function(event) {                 event.preventDefault();              var touch = event.targetTouches[0];              self._strokeUpdate(touch);              if (self.arePointsDisplayed) {                  var point = self._createPoint(touch);                  self._drawMark(point.x, point.y, 5);              }          };          this._handleTouchMove = _.throttle(_handleTouchMove, self.throttle, self.throttleOptions);          this._handleTouchEnd = function(event) {              var wasCanvasTouched = event.target === self._canvas;              if (wasCanvasTouched) {                  event.preventDefault();                  self._strokeEnd(event);              }          };          this._handleMouseEvents();          this._handleTouchEvents();      };      SignaturePad.prototype.clear = function() {          var ctx = this._ctx,              canvas = this._canvas;            ctx.fillStyle = this.backgroundColor;          ctx.clearRect(0, 0, canvas.width, canvas.height);          ctx.fillRect(0, 0, canvas.width, canvas.height);          this._reset();      };      SignaturePad.prototype.toDataURL = function(imageType, quality) {          var canvas = this._canvas;          return canvas.toDataURL.apply(canvas, arguments);      };      SignaturePad.prototype.fromDataURL = function(dataUrl) {          var self = this,              image = new Image(),              ratio = window.devicePixelRatio || 1,              width = this._canvas.width / ratio,              height = this._canvas.height / ratio;            this._reset();          image.src = dataUrl;          image.onload = function() {              self._ctx.drawImage(image, 0, 0, width, height);          };          this._isEmpty = false;      };      SignaturePad.prototype._strokeUpdate = function(event) {          var point = this._createPoint(event);          if(this._isPointToBeUsed(point)){              this._addPoint(point);          }      };      var pointsSkippedFromBeingAdded = 0;      SignaturePad.prototype._isPointToBeUsed = function(point) {          if(!this.minPointDistance)              return true;          var points = this.points;          if(points && points.length){              var lastPoint = points[points.length-1];              if(point.distanceTo(lastPoint) < this.minPointDistance){                    return false;              }          }          return true;      };      SignaturePad.prototype._strokeBegin = function(event) {          this._reset();          this._strokeUpdate(event);          if (typeof this.onBegin === ‘function’) {              this.onBegin(event);          }      };      SignaturePad.prototype._strokeDraw = function(point) {          var ctx = this._ctx,              dotSize = typeof(this.dotSize) === ‘function’ ? this.dotSize() : this.dotSize;            ctx.beginPath();          this._drawPoint(point.x, point.y, dotSize);          ctx.closePath();          ctx.fill();      };      SignaturePad.prototype._strokeEnd = function(event) {          var canDrawCurve = this.points.length > 2,              point = this.points[0];          if (!canDrawCurve && point) {              this._strokeDraw(point);          }          if (typeof this.onEnd === ‘function’) {              this.onEnd(event);          }      };      SignaturePad.prototype._handleMouseEvents = function() {          this._mouseButtonDown = false;            this._canvas.addEventListener(“mousedown”, this._handleMouseDown);          this._canvas.addEventListener(“mousemove”, this._handleMouseMove);          document.addEventListener(“mouseup”, this._handleMouseUp);      };     SignaturePad.prototype._handleTouchEvents = function() {             this._canvas.style.msTouchAction = ‘none’;          this._canvas.style.touchAction = ‘none’;          this._canvas.addEventListener(“touchstart”, this._handleTouchStart);          this._canvas.addEventListener(“touchmove”, this._handleTouchMove);          this._canvas.addEventListener(“touchend”, this._handleTouchEnd);      };      SignaturePad.prototype.on = function() {          this._handleMouseEvents();          this._handleTouchEvents();      };      SignaturePad.prototype.off = function() {          this._canvas.removeEventListener(“mousedown”, this._handleMouseDown);          this._canvas.removeEventListener(“mousemove”, this._handleMouseMove);          document.removeEventListener(“mouseup”, this._handleMouseUp);          this._canvas.removeEventListener(“touchstart”, this._handleTouchStart);          this._canvas.removeEventListener(“touchmove”, this._handleTouchMove);          this._canvas.removeEventListener(“touchend”, this._handleTouchEnd);      };      SignaturePad.prototype.isEmpty = function() {          return this._isEmpty;      };      SignaturePad.prototype._reset = function() {          this.points = [];          this._lastVelocity = 0;          this._lastWidth = (this.minWidth + this.maxWidth) / 2;          this._isEmpty = true;          this._ctx.fillStyle = this.penColor;      };      SignaturePad.prototype._createPoint = function(event) {          var rect = this._canvas.getBoundingClientRect();          return new Point(              event.clientX – rect.left,              event.clientY – rect.top          );      };      SignaturePad.prototype._addPoint = function(point) {          var points = this.points,              c2, c3,              curve, tmp;          points.push(point);          if (points.length > 2) {                        if (points.length === 3) points.unshift(points[0]);                tmp = this._calculateCurveControlPoints(points[0], points[1], points[2]);              c2 = tmp.c2;              tmp = this._calculateCurveControlPoints(points[1], points[2], points[3]);              c3 = tmp.c1;              curve = new Bezier(points[1], c2, c3, points[2]);              this._addCurve(curve);              points.shift();          }      };      SignaturePad.prototype._calculateCurveControlPoints = function(s1, s2, s3) {          var dx1 = s1.x – s2.x,              dy1 = s1.y – s2.y,              dx2 = s2.x – s3.x,              dy2 = s2.y – s3.y,              m1 = {                  x: (s1.x + s2.x) / 2.0,                  y: (s1.y + s2.y) / 2.0              },              m2 = {                  x: (s2.x + s3.x) / 2.0,                  y: (s2.y + s3.y) / 2.0              },              l1 = Math.sqrt(1.0 * dx1 * dx1 + dy1 * dy1),              l2 = Math.sqrt(1.0 * dx2 * dx2 + dy2 * dy2),              dxm = (m1.x – m2.x),              dym = (m1.y – m2.y),              k = l2 / (l1 + l2),              cm = {                  x: m2.x + dxm * k,                  y: m2.y + dym * k              },              tx = s2.x – cm.x,              ty = s2.y – cm.y;          return {              c1: new Point(m1.x + tx, m1.y + ty),              c2: new Point(m2.x + tx, m2.y + ty)          };      };      SignaturePad.prototype._addCurve = function(curve) {          var startPoint = curve.startPoint,              endPoint = curve.endPoint,              velocity, newWidth;          velocity = endPoint.velocityFrom(startPoint);          velocity = this.velocityFilterWeight * velocity +              (1 – this.velocityFilterWeight) * this._lastVelocity;          newWidth = this._strokeWidth(velocity);          this._drawCurve(curve, this._lastWidth, newWidth);          this._lastVelocity = velocity;          this._lastWidth = newWidth;      };      SignaturePad.prototype._drawPoint = function(x, y, size) {          var ctx = this._ctx;          ctx.moveTo(x, y);          ctx.arc(x, y, size, 0, 2 * Math.PI, false);          this._isEmpty = false;      };      SignaturePad.prototype._drawMark = function(x, y, size) {          var ctx = this._ctx;          ctx.save();          ctx.moveTo(x, y);          ctx.arc(x, y, size, 0, 2 * Math.PI, false);          ctx.fillStyle = ‘rgba(255, 0, 0, 0.2)’;          ctx.fill();          ctx.restore();      };      SignaturePad.prototype._drawCurve = function(curve, startWidth, endWidth) {          var ctx = this._ctx,              widthDelta = endWidth – startWidth,              drawSteps, width, i, t, tt, ttt, u, uu, uuu, x, y;          drawSteps = Math.floor(curve.length());          ctx.beginPath();          for (i = 0; i < drawSteps; i++) {                         t = i / drawSteps;              tt = t * t;              ttt = tt * t;              u = 1 – t;              uu = u * u;              uuu = uu * u;              x = uuu * curve.startPoint.x;              x += 3 * uu * t * curve.control1.x;              x += 3 * u * tt * curve.control2.x;              x += ttt * curve.endPoint.x;              y = uuu * curve.startPoint.y;              y += 3 * uu * t * curve.control1.y;              y += 3 * u * tt * curve.control2.y;              y += ttt * curve.endPoint.y;              width = startWidth + ttt * widthDelta;              this._drawPoint(x, y, width);          }          ctx.closePath();          ctx.fill();      };      SignaturePad.prototype._strokeWidth = function(velocity) {          return Math.max(this.maxWidth / (velocity + 1), this.minWidth);      };      var Point = function(x, y, time) {          this.x = x;          this.y = y;          this.time = time || new Date().getTime();      };      Point.prototype.velocityFrom = function(start) {          return (this.time !== start.time) ? this.distanceTo(start) / (this.time – start.time) : 1;      };      Point.prototype.distanceTo = function(start) {          return Math.sqrt(Math.pow(this.x – start.x, 2) + Math.pow(this.y – start.y, 2));      };      var Bezier = function(startPoint, control1, control2, endPoint) {          this.startPoint = startPoint;          this.control1 = control1;          this.control2 = control2;          this.endPoint = endPoint;      };      Bezier.prototype.length = function() {          var steps = 10,              length = 0,             i, t, cx, cy, px, py, xdiff, ydiff;          for (i = 0; i <= steps; i++) {              t = i / steps;              cx = this._point(t, this.startPoint.x, this.control1.x, this.control2.x, this.endPoint.x);              cy = this._point(t, this.startPoint.y, this.control1.y, this.control2.y, this.endPoint.y);              if (i > 0) {                  xdiff = cx – px;                  ydiff = cy – py;                  length += Math.sqrt(xdiff * xdiff + ydiff * ydiff);              }              px = cx;              py = cy;          }          return length;      };      Bezier.prototype._point = function(t, start, c1, c2, end) {          return start * (1.0 – t) * (1.0 – t) * (1.0 – t) +              3.0 * c1 * (1.0 – t) * (1.0 – t) * t +              3.0 * c2 * (1.0 – t) * t * t +              end * t * t * t;      };      return SignaturePad;  })(document);  var signaturePad = new SignaturePad(document.getElementById(‘signature-pad’), {      backgroundColor: ‘rgba(255, 255, 255, 0)’,      penColor: ‘rgb(0, 0, 0)’,      velocityFilterWeight: .7,      minWidth: 0.5,      maxWidth: 2.5,      throttle: 16,       minPointDistance: 3,  });  var clearButton = document.getElementById(‘clear’);  clearButton.addEventListener(‘click’, function(event) {      signaturePad.clear();  });  });  </script>  </body>  </html>  
Explanation:
In the above example, we have created a signature pad in HTML to draw signatures with the help of a mouse and a clear option to clear the signature pad.
Output:
Following is the output of this example:
HTML5 signature pad to image
Next TopicDifference between ‘hidden’ and ‘aria-hidden attributes in HTML
HTML5 signature pad to image

HTML5 signature pad to image

What do you mean by Signature pad?

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