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



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