Problems with toDataUrl

Question

I am trying to export to a text file the contents of a canvas with toDataUrl(), but I’m getting this mistake:

Domexception: Failed to execute 'toDataURL' on 'Htmlcanvaselement': Tainted canvases may not be Exported

I did some research and discovered that it is not possible to use the toDataUrl with images of "cross" origins, but the problem is that my image is local.

This is the current code:

const cnv = document.querySelector('canvas');
const ctx = cnv.getContext('2d');

const img = new Image;
img.src='./img/mydraw.png';

ctx.drawImage(img,0,0,300,140,0,0,300,140);
 
var image = cnv.toDataURL();
 
var blob = new Blob([image]);
saveAs(blob,'image.txt')