var SignaturePad = (function (document) {
"use strict";
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 (this.minWidth + this.maxWidth) / 2;
};
this.penColor = opts.penColor || "black";
this.backgroundColor = opts.backgroundColor || "rgba(0,0,0,0)";
this.onEnd = opts.onEnd;
this.onBegin = opts.onBegin;
this._canvas = canvas;
this._ctx = canvas.getContext("2d");
this.clear();
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();
this._reset();
image.src = dataUrl;
image.onload = function () {
self._ctx.drawImage(image, 0, 0, self._canvas.width, self._canvas.height);
};
this._isEmpty = false;
};
SignaturePad.prototype._strokeUpdate = function (event) {
var point = this._createPoint(event);
this._addPoint(point);
};
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 () {
var self = this;
this._mouseButtonDown = false;
this._canvas.addEventListener("mousedown", function (event) {
if (event.which === 1) {
self._mouseButtonDown = true;
self._strokeBegin(event);
}
});
this._canvas.addEventListener("mousemove", function (event) {
if (self._mouseButtonDown) {
self._strokeUpdate(event);
}
});
document.addEventListener("mouseup", function (event) {
if (event.which === 1 && self._mouseButtonDown) {
self._mouseButtonDown = false;
self._strokeEnd(event);
}
});
};
SignaturePad.prototype._handleTouchEvents = function () {
var self = this;
// Pass touch events to canvas element on mobile IE.
this._canvas.style.msTouchAction = 'none';
this._canvas.addEventListener("touchstart", function (event) {
var touch = event.changedTouches[0];
self._strokeBegin(touch);
});
this._canvas.addEventListener("touchmove", function (event) {
// Prevent scrolling.
event.preventDefault();
var touch = event.changedTouches[0];
self._strokeUpdate(touch);
});
document.addEventListener("touchend", function (event) {
var wasCanvasTouched = event.target === self._canvas;
if (wasCanvasTouched) {
self._strokeEnd(event);
}
});
};
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) {
// To reduce the initial lag make it work with 3 points
// by copying the first point to the beginning.
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);
// Remove the first element from the list,
// so that we always have no more than 4 points in points array.
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(dx1*dx1 + dy1*dy1),
l2 = Math.sqrt(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._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++) {
// Calculate the Bezier (x, y) coordinate for this step.
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;
};
// Returns approximated length.
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);
