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responsive-sketchpad.js
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responsive-sketchpad.js
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(function () {
function mergeObjects(obj1, obj2) {
var obj3 = {};
var attrname;
for (attrname in (obj1 || {})) {
if (obj1.hasOwnProperty(attrname)) {
obj3[attrname] = obj1[attrname];
}
}
for (attrname in (obj2 || {})) {
if (obj2.hasOwnProperty(attrname)) {
obj3[attrname] = obj2[attrname];
}
}
return obj3;
}
function Sketchpad(el, opts) {
var that = this;
if (!el) {
throw new Error('Must pass in a container element');
}
opts = opts || {};
var strokes = [];
var undos = [];
if (opts.data) {
opts.aspectRatio = opts.data.aspectRatio;
strokes = opts.data.strokes;
}
opts.aspectRatio = opts.aspectRatio || 1;
opts.width = opts.width || el.clientWidth;
opts.height = opts.height || opts.width * opts.aspectRatio;
opts.line = mergeObjects({
color: '#000',
size: 5,
cap: 'round',
join: 'round',
miterLimit: 10
}, opts.line);
// Boolean indicating if currently drawing
var sketching = false;
// Create a canvas element
var canvas = document.createElement('canvas');
/**
* Set the size of canvas
*/
function setCanvasSize (width, height) {
canvas.setAttribute('width', width);
canvas.setAttribute('height', height);
canvas.style.width = width + 'px';
canvas.style.height = height + 'px';
}
/**
* Get the size of the canvas
*/
function getCanvasSize () {
return {
width: canvas.width,
height: canvas.height
};
}
setCanvasSize(opts.width, opts.height);
el.appendChild(canvas);
var context = canvas.getContext('2d');
/**
* Returns a points x,y locations relative to the size of the canvase
*/
function getPointRelativeToCanvas (point) {
return {
x: point.x / canvas.width,
y: point.y / canvas.height
};
}
/**
* Returns true if is a touch event, false otherwise
*/
function isTouchEvent (e) {
return e.type.indexOf('touch') !== -1;
}
/**
* Get location of the cursor in the canvas
*/
function getCursorRelativeToCanvas (e) {
var cur = {};
if (isTouchEvent(e)) {
cur.x = e.touches[0].pageX - canvas.offsetLeft;
cur.y = e.touches[0].pageY - canvas.offsetTop;
} else {
var rect = that.canvas.getBoundingClientRect();
cur.x = e.clientX - rect.left;
cur.y = e.clientY - rect.top;
}
return getPointRelativeToCanvas(cur);
}
/**
* Get the line size relative to the size of the canvas
* @return {[type]} [description]
*/
function getLineSizeRelativeToCanvas (size) {
return size / canvas.width;
}
/**
* Erase everything in the canvase
*/
function clearCanvas () {
context.clearRect(0, 0, canvas.width, canvas.height);
if (opts.backgroundColor) {
context.fillStyle = opts.backgroundColor;
context.fillRect(0, 0, canvas.width, canvas.height);
}
}
/**
* Since points are stored relative to the size of the canvas
* this takes a point and converts it to actual x, y distances in the canvas
*/
function normalizePoint (point) {
return {
x: point.x * canvas.width,
y: point.y * canvas.height
};
}
/**
* Since line sizes are stored relative to the size of the canvas
* this takes a line size and converts it to a line size
* appropriate to the size of the canvas
*/
function normalizeLineSize (size) {
return size * canvas.width;
}
/**
* Draw a stroke on the canvas
*/
function drawStroke (stroke) {
context.beginPath();
for (var j = 0; j < stroke.points.length - 1; j++) {
var start = normalizePoint(stroke.points[j]);
var end = normalizePoint(stroke.points[j + 1]);
context.moveTo(start.x, start.y);
context.lineTo(end.x, end.y);
}
context.closePath();
context.strokeStyle = stroke.color;
context.lineWidth = normalizeLineSize(stroke.size);
context.lineJoin = stroke.join;
context.lineCap = stroke.cap;
context.miterLimit = stroke.miterLimit;
context.stroke();
}
/**
* Redraw the canvas
*/
function redraw () {
clearCanvas();
for (var i = 0; i < that.strokes.length; i++) {
drawStroke(that.strokes[i]);
}
}
// On mouse down, create a new stroke with a start location
function startLine (e) {
e.preventDefault();
strokes = that.strokes;
sketching = true;
that.undos = [];
var cursor = getCursorRelativeToCanvas(e);
strokes.push({
points: [cursor],
color: opts.line.color,
size: getLineSizeRelativeToCanvas(opts.line.size),
cap: opts.line.cap,
join: opts.line.join,
miterLimit: opts.line.miterLimit
});
}
function drawLine (e) {
if (!sketching) {
return;
}
e.preventDefault();
var cursor = getCursorRelativeToCanvas(e);
that.strokes[strokes.length - 1].points.push({
x: cursor.x,
y: cursor.y
});
that.redraw();
}
function endLine (e) {
if (!sketching) {
return;
}
e.preventDefault();
sketching = false;
if (isTouchEvent(e)) {
return; // touchend events do not have a cursor position
}
var cursor = getCursorRelativeToCanvas(e);
that.strokes[strokes.length - 1].points.push({
x: cursor.x,
y: cursor.y
});
that.redraw();
if (that.onDrawEnd) that.onDrawEnd();
}
// Event Listeners
canvas.addEventListener('mousedown', startLine);
canvas.addEventListener('touchstart', startLine);
canvas.addEventListener('mousemove', drawLine);
canvas.addEventListener('touchmove', drawLine);
canvas.addEventListener('mouseup', endLine);
canvas.addEventListener('mouseleave', endLine);
canvas.addEventListener('touchend', endLine);
if (typeof opts.onDrawEnd === 'function') {
this.onDrawEnd = opts.onDrawEnd;
}
// Public variables
this.canvas = canvas;
this.strokes = strokes;
this.undos = undos;
this.opts = opts;
// Public functions
this.redraw = redraw;
this.setCanvasSize = setCanvasSize;
this.getPointRelativeToCanvas = getPointRelativeToCanvas;
this.getLineSizeRelativeToCanvas = getLineSizeRelativeToCanvas;
if (strokes) {
redraw();
}
}
/**
* Undo the last action
*/
Sketchpad.prototype.undo = function () {
if (this.strokes.length === 0){
return;
}
this.undos.push(this.strokes.pop());
this.redraw();
};
/**
* Redo the last undo action
*/
Sketchpad.prototype.redo = function () {
if (this.undos.length === 0) {
return;
}
this.strokes.push(this.undos.pop());
this.redraw();
};
/**
* Clear the sketchpad
*/
Sketchpad.prototype.clear = function () {
this.undos = []; // TODO: Add clear action to undo
this.strokes = [];
this.redraw();
};
/**
* Convert the sketchpad to a JSON object that can be loaded into
* other sketchpads or stored on a server
*/
Sketchpad.prototype.toJSON = function () {
return {
aspectRatio: this.canvas.width / this.canvas.height,
strokes: this.strokes
};
};
/**
* Load a json object into the sketchpad
* @return {object} - JSON object to load
*/
Sketchpad.prototype.loadJSON = function (data) {
this.strokes = data.strokes;
this.redraw();
};
/**
* Set the line size
* @param {number} size - Size of the brush
*/
Sketchpad.prototype.setLineSize = function (size) {
this.opts.line.size = size;
};
/**
* Set the line color
* @param {string} color - Hexadecimal color code
*/
Sketchpad.prototype.setLineColor = function (color) {
this.opts.line.color = color;
};
/**
* Draw a line
* @param {object} start - Starting x and y locations
* @param {object} end - Ending x and y locations
* @param {object} lineOpts - Options for line (color, size, etc.)
*/
Sketchpad.prototype.drawLine = function (start, end, lineOpts) {
lineOpts = mergeObjects(this.opts.line, lineOpts);
start = this.getPointRelativeToCanvas(start);
end = this.getPointRelativeToCanvas(end);
this.strokes.push({
points: [start, end],
color: lineOpts.color,
size: this.getLineSizeRelativeToCanvas(lineOpts.size),
cap: lineOpts.cap,
join: lineOpts.join,
miterLimit: lineOpts.miterLimit
});
this.redraw();
};
/**
* Resize the canvas maintaining original aspect ratio
* @param {number} width - New width of the canvas
*/
Sketchpad.prototype.resize = function (width) {
var height = width * this.opts.aspectRatio;
this.opts.lineSize = this.opts.lineSize * (width / this.opts.width);
this.opts.width = width;
this.opts.height = height;
this.setCanvasSize(width, height);
this.redraw();
};
if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
module.exports = Sketchpad;
} else {
window.Sketchpad = Sketchpad;
}
})();