Error: canvas.toDataURL() is not a function

[Prajwal Sapare]

Currently I am trying to convert browser based client side volume rendering code to server side pure javascript based rendering.

I use node-webgl at server side. My main goal is to send the canvas content of server to client, later this image data is displayed on the client.

But before this I need to check whether the rendering is proper. So I used canvas.toDataURL() to extract canvas data and want to display it on a separate window. But I am facing the error.

Below is my code:

Entry point javascript code:

var nodejs=true,

WebGL = require('./node_modules/node-webgl/index'),
document = WebGL.document();

document.setTitle("Lesson02");
requestAnimationFrame = document.requestAnimationFrame;
alert=console.error;

//Read and eval library
fs=require('fs');
eval(fs.readFileSync(__dirname+ '/sylvester.js','utf8'));
eval(fs.readFileSync(__dirname+ '/glUtils.js','utf8'));
eval(fs.readFileSync(__dirname+ '/glAux.js','utf8'));
eval(fs.readFileSync(__dirname+ '/volumercserver.js','utf8'));

volumerc_main('./raycast-color.frag','./aorta-high512.jpg','./tfold.png');

volumetricserver.js excerpt:

var Image = require("node-webgl").Image;

var canvas = document.createElement("canvas");

canvas.id = 'canvas_win';

canvas.width= 512;

canvas.height= 512;

var gl;

var canvas1 = document.createElement("canvas");

canvas1.width= 512;

canvas1.height= 512;

var ctx = canvas1.getContext('2d');

try {

    gl = canvas.getContext("webgl", {premultipliedAlpha: false}) ||    canvas.getContext("experimental-webgl",{premultipliedAlpha: false});

} catch (e) {

}

if (!gl) {

    alert("Could not initialise WebGL, sorry :-(");

}   

// All computations take place here

//................

//..................

//.............

     var dataURLstring = canvas.toDataURL();

     var img1 = new Image;

     img1.src = dataURLstring;

    // img1.onload = function(){

     ctx.drawImage(img1,0,0); // Or at whatever offset you like

    // };

Error:

C:\Users\z003npra\Desktop\node>node exp.js

Status: Using GLEW 1.13.0

Status: Using GLEW 1.13.0

I am here

undefined:457

                var dataURLstring = canvas.toDataURL();

                                           ^

TypeError: canvas.toDataURL is not a function

    at drawVolume (eval at <anonymous> (C:\Users\z003npra\Desktop\node\exp.js:18

:9), <anonymous>:457:30)

    at Timer.listOnTimeout (timers.js:92:15)

Please let me the issue. Is toDataURL not supported in node-WebGL? any alternative?

Regards,

Prajwal