Save html5 canvas element to file (local)

Question

I'm doing a webapp on Android, and I've a HTML5 Canvas on which an user can draw what he wants using touch events. And I would like to save this on a sdcard, so in local. And can't use any server side script (php etc) to do that stuff.

I'm using a magictouch.js example :

    <canvas id="example" height=450 width=300></canvas> 
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script> 
    <script type="text/javascript" src="magictouch.js"></script>

    <script> 

    var CanvasDrawr = function(options) {

    var canvas = document.getElementById(options.id),
    ctxt = canvas.getContext("2d");
    var img     = canvas.toDataURL("image/png");


    ctxt.lineWidth = options.size || Math.ceil(Math.random() * 35);
    ctxt.lineCap = options.lineCap || "round";
    ctxt.pX = undefined;
    ctxt.pY = undefined;

    var lines = [,,];
     var offset = $(canvas).offset();

    var self = {
    //bind click events
    init: function() {

    canvas.addEventListener('touchstart', self.preDraw, false);
    canvas.addEventListener('touchmove', self.draw, false);

    },

    preDraw: function(event) {
            $.each(event.touches, function(i, touch) {
              var id = touch.identifier;
              lines[id] = { x     : this.pageX - offset.left, 
                y     : this.pageY - offset.top, 
                color : options.color || ["black"] 
              };
    });

    event.preventDefault();
  },

  draw: function(event) {
    var e = event, hmm = {};

    $.each(event.touches, function(i, touch) {
      var id = touch.identifier;
      var moveX = this.pageX - offset.left - lines[id].x,
      moveY = this.pageY - offset.top - lines[id].y;

      var ret = self.move(id, moveX, moveY);
      lines[id].x = ret.x;
      lines[id].y = ret.y;
    });

    event.preventDefault();
  },

  move: function(i, changeX, changeY) {
    ctxt.strokeStyle = lines[i].color;
    ctxt.beginPath();
    ctxt.moveTo(lines[i].x, lines[i].y);

    ctxt.lineTo(lines[i].x + changeX, lines[i].y + changeY);
    ctxt.stroke();
    ctxt.closePath();

    return { x: lines[i].x + changeX, y: lines[i].y + changeY };
  }
};

    return self.init();
    };

    $(function(){
var super_awesome_multitouch_drawing_canvas_thingy = new CanvasDrawr({id:"example", size: 2 }); 
console.log('loaded');
      });

    </script> 
    </body>

But all examples which I met on Internet were used with a php script on a server to decode and save the canva as an image. And actually just want to do that on my Android device, in my sdcard, by just using HTML5/Javascript...

Thanks.

Answer 1

Did you check nihilogic library ? http://www.nihilogic.dk/labs/canvas2image/

It use toDataUrl() function so you may get an ugly name of pictures but still you will have a picture.

You also can use downloadify but it use flash and I know flash is not often on android, depend your case https://github.com/dcneiner/Downloadify

Also I, like kbok, don't know phoneGap but you could probably try to use both context.toDataUrl() and fwrite.