Comment ajouter une fonctionnalité d'annulation à la toile HTML5?

Voici une solution qui fonctionne pour moi. Je l'ai essayé dans les dernières versions de Firefox et Chrome et cela fonctionne vraiment bien dans ces deux navigateurs.

var isFirefox = typeof InstallTrigger !== 'undefined';
var ctx = document.getElementById('myCanvas').getContext("2d");
var CanvasLogBook = function() {
    this.index = 0;
    this.logs = [];
    this.logDrawing();
};
CanvasLogBook.prototype.sliceAndPush = function(imageObject) {
    var array;
    if (this.index == this.logs.length-1) {
        this.logs.push(imageObject);
        array = this.logs;
    } else {
        var tempArray = this.logs.slice(0, this.index+1);
        tempArray.push(imageObject);
        array = tempArray;
    }
    if (array.length > 1) {
        this.index++;
    }
    return array;
};
CanvasLogBook.prototype.logDrawing = function() { 
    if (isFirefox) {
        var image = new Image();
        image.src = document.getElementById('myCanvas').toDataURL();
        this.logs = this.sliceAndPush(image);
    } else {
        var imageData = document.getElementById('myCanvas').toDataURL();
        this.logs = this.sliceAndPush(imageData);
    }
};
CanvasLogBook.prototype.undo = function() {
    ctx.clearRect(0, 0, $('#myCanvas').width(), $('#myCanvas').height());
    if (this.index > 0) {
        this.index--;
        this.showLogAtIndex(this.index);
    }
};
CanvasLogBook.prototype.redo = function() {
    if (this.index < this.logs.length-1) {
        ctx.clearRect(0, 0, $('#myCanvas').width(), $('#myCanvas').height());
        this.index++;
        this.showLogAtIndex(this.index);
    }
};
CanvasLogBook.prototype.showLogAtIndex = function(index) {
    ctx.clearRect(0, 0, $('#myCanvas').width(), $('#myCanvas').height());
    if (isFirefox) {
        var image = this.logs[index];
        ctx.drawImage(image, 0, 0);
    } else {
        var image = new Image();
        image.src = this.logs[index];
        ctx.drawImage(image, 0, 0);
    }
};
var canvasLogBook = new CanvasLogBook();