'Tainted canvases may not be exported' when using drawImage

Question

When trying to draw an image onto a canvas, and then saving the canvas to an image, I get the following error:

Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported

var picture = new Image();
picture.src = "https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Smiley.svg/800px-Smiley.svg.png";
var canvas = document.getElementById("background");
var context = canvas.getContext("2d");
function generate(){
 var ctx = document.createElement("canvas").getContext("2d");
  ctx.canvas.width = canvas.width;
  ctx.canvas.height = canvas.height;
 ctx.fillStyle = "red"; 
 ctx.rect (0, 0, 40, 40);
 ctx.fill();

 ctx.drawImage(picture,0,0);
 
 image = new Image();
 image.setAttribute('crossOrigin', 'anonymous');
 image.src = ctx.canvas.toDataURL("image/png");  
}
function draw(){
 context.clearRect(0, 0, canvas.width, canvas.height);
 context.drawImage(image, 0,0,100,100,0,0,100,100); 
}
function play(){
  generate();
  setInterval(function(){draw();}, 0.0333);
}

window.onload = function(){
 if(picture.complete)play();
 else picture.onload = play; 
}

<canvas id="background" width=500 height=500></canvas>

I know it's to do with drawing the image on the canvas because when that line is removed everything's okay and you can see the red box:

var picture = new Image();
picture.src = "https://upload.wikimedia.org/wikipedia/commons/thumb/8/85/Smiley.svg/800px-Smiley.svg.png";
var canvas = document.getElementById("background");
var context = canvas.getContext("2d");
function generate(){
 var ctx = document.createElement("canvas").getContext("2d");
  ctx.canvas.width = canvas.width;
  ctx.canvas.height = canvas.height;
 ctx.fillStyle = "red"; 
 ctx.rect (0, 0, 40, 40);
 ctx.fill();
 
 image = new Image();
 image.setAttribute('crossOrigin', 'anonymous');
 image.src = ctx.canvas.toDataURL("image/png");  
}
function draw(){
 context.clearRect(0, 0, canvas.width, canvas.height);
 context.drawImage(image, 0,0,100,100,0,0,100,100); 
}
function play(){
  generate();
  setInterval(function(){draw();}, 0.0333);
}

window.onload = function(){
 if(picture.complete)play();
 else picture.onload = play; 
}

<canvas id="background" width=500 height=500></canvas>

So it's drawImage that causes this to fail.

I've read other questions and the solutions were "just add image.setAttribute('crossOrigin', 'anonymous');" (which I've done) or to put them in the same directory (I tried this by placing both files on desktop) but neither seemed to solve it for me.

Is there a fix or an alternative method? All I want to do is draw multiple images onto one image. (The red box was just for show.)

Answer 1

I tried this by placing both files on desktop

No. You need a web server and to open your files in http:// (or https://) for them to be considered of the same origin. When you open your files in file://, they're not considered of the same origin, even if you serve them from the same directory.