Tainted canvases may not be exported

Question

I want to save my canvas to a img  I have this function   function save         document getElementById  canvasimg   style border    2px solid       var dataURL   canvas toDataURL        document getElementById  canvasimg   src   dataURL      document getElementById  canvasimg   style display    inline       It gives me error      Uncaught SecurityError  Failed to execute  toDataURL  on  HTMLCanvasElement   Tainted canvases may not be exported    What should I do

User · Answer

I also solved this error by adding useCORS   true  in my code like -  html2canvas     chart-section   0             useCORS   true          allowTaint   true          scale   0 98          dpi   500          width  1400  height  900        then

User · Answer

If you re using ctx drawImage   function  you can do the following   var img   loadImage     yourimage png   callback    function loadImage src  callback        var img   new Image         img onload   callback      img setAttribute  crossorigin    anonymous       works for me      img src   src       return img      And in your callback you can now use ctx drawImage and export it using toDataURL

User · Answer

In the img tag set crossorigin to Anonymous    lt img crossorigin  anonymous  gt  lt  img gt

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For security reasons  your local drive is declared to be  other-domain  and will taint the canvas    That s because your most sensitive info is likely on your local drive     While testing try these workarounds    Put all page related files   html   jpg   js   css  etc  on your desktop  not in sub-folders   Post your images to a site that supports cross-domain sharing  like dropbox com    Be sure you put your images in dropbox s public folder and also set the cross origin flag when downloading the image  var img new Image    img crossOrigin  anonymous       Install a webserver on your development computer  IIS and PHP web servers both have free editions that work nicely on a local computer

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Check out CORS enabled image from MDN  Basically you must have a server hosting images with the appropriate Access-Control-Allow-Origin header   x000D   x000D   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  x000D   x000D   x000D   You will be able to save those images to DOM Storage as if they were served from your domain otherwise you will run into security issue   x000D   x000D  var img   new Image      canvas   document createElement  canvas        ctx   canvas getContext  2d        src    http   example com image      insert image url here  img crossOrigin    Anonymous    img onload   function         canvas width   img width      canvas height   img height      ctx drawImage  img  0  0        localStorage setItem   savedImageData   canvas toDataURL  image png        img src   src     make sure the load event fires for cached images too if   img complete    img complete     undefined         img src    data image gif base64 R0lGODlhAQABAIAAAAAAAP   ywAAAAAAQABAAACAUwAOw         img src   src    x000D   x000D   x000D

User · Answer

I resolved the problem using useCORS  true option   html2canvas document getElementsByClassName  droppable-area   0     useCORS true   then function  canvas           var imgBase64   canvas toDataURL               console log  imgBase64    imgBase64           var imgURL    data image     imgBase64          var triggerDownload       lt a gt    attr  href   imgURL  attr  download    layout   new Date   getTime     jpeg   appendTo  body            triggerDownload 0  click            triggerDownload remove

User · Answer

Seems like you are using an image from a URL that has not set correct Access-Control-Allow-Origin header and hence the issue   You can fetch that image from your server and get it from your server to avoid CORS issues

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In my case I was drawing onto a canvas tag from a video  To address the tainted canvas error I had to do two things    lt video id  video source  crossorigin  anonymous  gt       lt source src  http   crossdomain example com myfile mp4  gt   lt  video gt     Ensure Access-Control-Allow-Origin header is set in the video source response  proper setup of crossdomain example com  Set the video tag to have crossorigin  anonymous

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If someone views on my answer  you maybe in this condition  1  Trying to get a map screenshot in canvas using openlayers  version  gt   3  2  And viewed the example of exporting map 3  Using ol source XYZ to render map layer Bingo  Using ol source XYZ crossOrigin    Anonymous  to solve your confuse  Or like following code       var baseLayer   new ol layer Tile            name   basic            source  new ol source XYZ                url  options baseMap basic               crossOrigin   quot Anonymous quot

User · Answer

Just as a build on  markE s answer   if you want to create a local server  You won t have this error on a local server  If you have PHP installed on your computer   Open up your terminal cmd Navigate into the folder where your website files are While in this folder  run the command php -S localhost 3000   Notice the capital  S  Open up your browser and in the URL bar go to localhost 3000  Your website should be running there   or If you have Node js installed on your computer   Open up your terminal cmd Navigate into the folder where your website files are While in this folder  run the command npm init -y Run npm install live-server -g or sudo npm install live-server -g on a mac Run live-server and it should automatically open up a new tab in the browser with your website open   Note  remember to have an index html file in the root of your folder or else you might have some issues

[javascript] Tainted canvases may not be exported

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