Javascript – Uploading a canvas image to facebook as Blob of multipart/form-data type

facebookfacebook-javascript-sdkimagejavascriptpost

I am trying to use the facebook api to upload an image from a canvas I save on the page:

var file = dataURItoBlob(canvas.toDataURL('image/jpeg', 1.0))

FB.api('/me/photos', 'POST', {
  source: file,
  message: 'photo description'
}, function (response) {
    console.log(response)
  }
)

This is the blob convertor:

function dataURItoBlob(dataURI) {
  var byteString = atob(dataURI.split(',')[1]);
  var ab = new ArrayBuffer(byteString.length);
  var ia = new Uint8Array(ab);
  for (var i = 0; i < byteString.length; i++) {
    ia[i] = byteString.charCodeAt(i);
  }
  return new Blob([ab], { type: 'image/jpeg' });
}

And I am getting an error: message: "(#324) Requires upload file" so it seems the uploader does not recognize the blob as a valid file.

UPDATE 1:

I fount this post: Convert Data URI to File then append to FormData about converting blob to formData, tried it like this:

var dataURL = canvas.toDataURL('image/jpeg', 1.0)
var blob = dataURItoBlob(dataURL)
var fd = new FormData(document.forms[0])
fd.append("canvasImage", blob)

FB.api('/me/photos', 'POST', {
  source: fd .....

But still the same error.

UPDATE 2:

Even tried this XHR post solution, Using Facebooks javascript api to post multipart/form-data encoded image and still getting file issue "Your photos couldn't be uploaded. Photos should be less than 4 MB and saved as JPG, PNG, GIF or TIFF files."

function postImageToFacebook(access_token) {
  var filename = "samplepic.png",
    mimeType = "image/png",
    message = "test comment",
    data = canvas.toDataURL("image/png"),
    encodedPng = data.substring(data.indexOf(',') + 1, data.length),
    imageData = atob(encodedPng);

  // build the multipart/form-data
  var boundary = '----ThisIsTheBoundary1234567890';
  var formData = '--' + boundary + '\r\n'
  formData += 'Content-Disposition: form-data; name="source"; filename="' + filename + '"\r\n';
  formData += 'Content-Type: ' + mimeType + '\r\n\r\n';
  for (var i = 0; i < imageData.length; ++i) {
    formData += String.fromCharCode(imageData[i] & 0xff);
  }
  formData += '\r\n';
  formData += '--' + boundary + '\r\n';
  formData += 'Content-Disposition: form-data; name="message"\r\n\r\n';
  formData += message + '\r\n'
  formData += '--' + boundary + '--\r\n';

  var xhr = new XMLHttpRequest();
  xhr.open( 'POST', 'https://graph.facebook.com/v2.5/me/photos?access_token=' + access_token, true );
  xhr.onload = xhr.onerror = function() {
    console.log( xhr.responseText );
  };
  xhr.setRequestHeader( "Content-Type", "multipart/form-data; boundary=" + boundary );
  xhr.send( formData );
}

Best Answer

I figured out, for some reason, the issues was the headers that I tried to apply as a solution for a previous problem... Here is a working solution: https://jsfiddle.net/ilyador/vyne7oh2/8/

function fbUpload(token){
  var dataURL = canvas.toDataURL('image/jpeg', 1.0)
  var blob = dataURItoBlob(dataURL)
  var formData = new FormData()
  formData.append('token', token)
  formData.append('source', blob)

  var xhr = new XMLHttpRequest();
  xhr.open( 'POST', 'https://graph.facebook.com/me/photos', true )
  xhr.onload = xhr.onerror = function() {
    console.log( xhr.responseText )
  };
  xhr.send( formData )
}

function dataURItoBlob(dataURI) {
  var byteString = atob(dataURI.split(',')[1]);
  var ab = new ArrayBuffer(byteString.length);
  var ia = new Uint8Array(ab);
  for (var i = 0; i < byteString.length; i++) { ia[i] = byteString.charCodeAt(i); }
  return new Blob([ab], { type: 'image/jpeg' });
}
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