Pass image between canvas with Webrtc

Question

I have found a similar question but it doesn't seem to answer my question. I have an HTML5 canvas and i use pubnub with webrtc. What i want to do is to pass my image between the canvas like the data from here are passed http://pubnub.github.io/codoodler/history.html. Any ideas? (Please add an example to the answer if possible)

! function() {
    function a(a) {
        q.publish({
            channel: 'mychannel12',
            message: a
        })
    }

    function b(a, b) {
        h.strokeStyle = a, h.beginPath(), h.moveTo(b[0].x, b[0].y);
        for (var c = 1; c < b.length; c++) h.lineTo(b[c].x, b[c].y);
        h.stroke()
    }

    function c(a) {
        !a || a.plots.length < 1 || b(a.color, a.plots)
    }

    function d(a) {
        if (a.preventDefault(), r) {
            var c = j ? a.targetTouches[0].pageX - g.offsetLeft : a.offsetX || a.layerX - g.offsetLeft,
                d = j ? a.targetTouches[0].pageY - g.offsetTop : a.offsetY || a.layerY - g.offsetTop;
            s.push({
                x: c << 0,
                y: d << 0
            }), b(i, s)
        }
    }

    function e(a) {
        a.preventDefault(), r = !0
    }

    function f(b) {
        b.preventDefault(), r = !1, a({
            color: i,
            plots: s
        }), s = []
    }
    var g = document.getElementById("drawCanvas"),
        h = g.getContext("2d"),
        i = document.querySelector(":checked").getAttribute("data-color");
    g.width = Math.min(document.documentElement.clientWidth, window.innerWidth || 300), g.height = Math.min(document.documentElement.clientHeight, window.innerHeight || 300), h.strokeStyle = i, h.lineWidth = "3", h.lineCap = h.lineJoin = "round", document.getElementById("colorSwatch").addEventListener("click", function() {
        i = document.querySelector(":checked").getAttribute("data-color")
    }, !1);
    var j = "ontouchstart" in window,
        k = navigator.pointerEnabled,
        l = navigator.msPointerEnabled,
        m = j ? "touchstart" : k ? "pointerdown" : l ? "MSPointerDown" : "mousedown",
        n = j ? "touchmove" : k ? "pointermove" : l ? "MSPointerMove" : "mousemove",
        o = j ? "touchend" : k ? "pointerup" : l ? "MSPointerUp" : "mouseup";
    g.addEventListener(m, e, !1), g.addEventListener(n, d, !1), g.addEventListener(o, f, !1);
    var p = "draw",
        q = PUBNUB.init({
            publish_key: "pub-c-465c4b3b-0b7d-40de-86c5-10a9433058b5",
            subscribe_key: "sub-c-43a257e0-d94a-11e4-a2b8-0619f8945a4f",
            leave_on_unload: !0
        });
    q.subscribe({
        channel: 'mychannel12',
        callback: c,
        presence: function(a) {
            a.occupancy > 1 && (document.getElementById("unit").textContent = "doodlers"), document.getElementById("occupancy").textContent = a.occupancy;
            var b = document.getElementById("occupancy").parentNode;
            b.classList.add("anim"), b.addEventListener("transitionend", function() {
                b.classList.remove("anim")
            }, !1)
        }
    }), drawHistory && q.history({
        channel: 'mychannel12',
        count: 50,
        callback: function(a) {
            q.each(a[0], c)
        }
    });
    var r = !1,
        s = []
}();

Answer 1

You can publish/subscribe the canvas coordinates data in (x, y), just like the code sample, or pass the url/path of the image, but not the image itself.

The size of each data you can publish using PubNub APIs is <32k, so passing images directly using PubNub is not an ideal way, even if you convert a canvas image to a base64 with canvas.toDataURL. It would be still too large.

You probably want to send the canvas images data elsewhere, like Parse, and just pass the url.