How to fix getImageData error The canvas has been tainted by cross-origin data

Question

My code is working very well on my localhost but it is not working on the site   I got this error from the console  for this line  getImageData x y 1 1  data   Uncaught SecurityError  Failed to execute  getImageData  on  CanvasRenderingContext2D   The canvas has been tainted by cross-origin data     part of my code   jQuery Event prototype rgb function            var x    this offsetX     this pageX -   this target  offset   left  y    this offsetY     this pageY -   this target  offset   top           if  this target nodeName    CANVAS  return null          return this target getContext  2d   getImageData x y 1 1  data          Note  my image url  src  is from a subdomain url

User · Answer

I found that I had to use  setAttribute  crossOrigin       and had to append a timestamp to the URL s query string to avoid a 304 response lacking the Access-Control-Allow-Origin header    This gives me  var url    http   lorempixel com g 400 200    var imgObj   new Image    imgObj src   url         new Date   getTime    imgObj setAttribute  crossOrigin

User · Answer

As others have said you are  tainting  the canvas by loading from a cross origins domain   https   developer mozilla org en-US docs HTML CORS Enabled Image  However  you may be able to prevent this by simply setting   img crossOrigin    Anonymous     This only works if the remote server sets the following header appropriately   Access-Control-Allow-Origin       The Dropbox file chooser when using the  direct link  option is a great example of this  I use it on oddprints com to hoover up images from the remote dropbox image url  into my canvas  and then submit the image data back into my server  All in javascript

User · Answer

When working on local add a server I had a similar issue when working on local  You url is going to be the path to the local file e g  file    Users PeterP Desktop folder index html  Please note that I am on a MAC  I got round this by installing http-server globally  https   www npmjs com package http-server Steps   Global install  npm install http-server -g Run server  http-server   Desktop folder   PS  I assume you have node installed  otherwise you wont get very far running npm commands

User · Answer

I meet the same problem today  and solve it by the code follows   html code    lt div style  display  none  gt     lt img id  img  src  img iak png  width  600  height  400    gt   lt  div gt   lt canvas id  iak  gt broswer don t support canvas lt  canvas gt    js code   var canvas   document getElementById  iak   var iakImg   document getElementById  img   var ctx   canvas getContext  2d   var image   new Image   image src iakImg src image onload   function         ctx drawImage image 0 0     var data   ctx getImageData 0 0 600 400      code like above  and there is no cross-domain problem

User · Answer

I was having the same issue  and for me it worked by simply concatenating https   image getAttribute  src

User · Answer

You are  tainting  the canvas by loading from a cross origins domain  Check out this MDN article   https   developer mozilla org en-US docs HTML CORS Enabled Image

User · Answer

I was seeing this error on Chrome while I was testing my code locally  I switched to Firefox and I am not seeing the error any more  Maybe switching to another browser is a quick fix   If you are using the solution given in first answer  then make sure you add img crossOrigin    Anonymous   just after you declare the img variable  for eg  var img   new Image

User · Answer

Your problem is that you load an external image  meaning from another domain  This causes a security error when you try to access any data of your canvas context

User · Answer

As matt burns says in his answer  you may need to enable CORS on the server where the problem images are hosted   If the server is Apache  this can be done by adding the following snippet  from here  to either your VirtualHost config or an  htaccess file    lt IfModule mod setenvif c gt       lt IfModule mod headers c gt           lt FilesMatch     cur gif ico jpe g png svgz  webp    gt              SetEnvIf Origin     IS CORS             Header set Access-Control-Allow-Origin     env IS CORS          lt  FilesMatch gt       lt  IfModule gt   lt  IfModule gt       if adding it to a VirtualHost  you ll probably need to reload Apache s config too  eg  sudo service apache2 reload if Apache s running on a Linux server

User · Answer

My problem was so messed up I just base64 encoded the image to ensure there couldn t be any CORS issues

User · Answer

You won t be able to draw images directly from another server into a canvas and then use getImageData  It s a security issue and the canvas will be considered  tainted    Would it work for you to save a copy of the image to your server using PHP and then just load the new image  For example  you could send the URL to the PHP script and save it to your server  then return the new filename to your javascript like this    lt  php   The name of this file in this example is imgdata php     url   GET  url          prevent hackers from uploading PHP scripts and pwning your system   if   is array getimagesize  url         echo  path to placeholderImage png       exit  wrong file type             img   file get contents  url       fn   substr strrchr  url        1     file put contents  fn  img     echo  fn     gt    You d use the PHP script with some ajax javascript like this   xi new XMLHttpRequest    xi open  GET   imgdata php url   yourImageURL true   xi send     xi onreadystatechange function       if xi readyState  4  amp  amp  xi status  200        img new Image      img onload function           ctx drawImage img  0  0  canvas width  canvas height             img src xi responseText          If you use getImageData on the canvas after that  it will work fine    Alternatively  if you don t want to save the whole image  you could pass x  amp  y coordinates to your PHP script and calculate the pixel s rgba value on that side  I think there are good libraries for doing that kind of image processing in PHP   If you want to use this approach  let me know if you need help implementing it   edit-1  peeps pointed out that the php script is exposed and allows the internet to potentially use it maliciously  there are a million ways to handle this  one of the simplest being some sort of URL obfuscation    i reckon secure php practices deserves a separate google  P  edit-2  by popular demand  I ve added a check to ensure it is an image and not a php script  from  PHP check if file is an image

[javascript] How to fix getImageData() error The canvas has been tainted by cross-origin data?

Examples related to javascript

Examples related to html

Examples related to html5-canvas