Unable to correctly upload images using the Dropbox API in Matlab

[reseda333]

I am trying to upload an image to Dropbox using the Dropbox API and Matlab's webwrite function.  I get a successful response when running the below code. However, the response says 'size: 215' when I know the size of the image should be lower than that. Furthermore, the image uploaded to Dropbox appears to be corrupted. It does not preview, and after I download and try to open the uploaded image, it does not register as a valid image. I think the issue might have something to do with the encoding, but I can't figure it out. When I use this same code to upload a plain text file with ASCII characters, it works without any problem. Does anyone know what the problem might be?

% Read the file from disk

fid = fopen(dataFile, 'r');

data = char(fread(fid)');

fclose(fid);

[~,remoteFName, remoteExt] = fileparts(dataFile);

headerFields = {'Authorization', ['Bearer ', dropboxAccessToken]};

headerFields{2,1} = 'Dropbox-API-Arg';

headerFields{2,2} = sprintf('{"path": "/%s%s", "mode": "add", "autorename": true, "mute": false}',remoteFName, remoteExt);

headerFields{3,1} = 'Content-Type';

headerFields{3,2} = 'application/octet-stream';

headerFields = string(headerFields);

% Set the options for WEBWRITE

opt = weboptions;

opt.MediaType = 'application/octet-stream';

opt.CharacterEncoding = 'ISO-8859-1';

opt.RequestMethod = 'post';

opt.HeaderFields = headerFields;

% Upload the file

try

   tempOutput = webwrite('https://content.dropboxapi.com/2/files/upload', data, opt);

catch someException

   disp(someException);

   throw(addCause(MException('uploadToDropbox:unableToUploadFile','Unable to upload file.'),someException));

end

RESPONSE

HTTP/1.1 200 OK
Cache-Control: no-cache
X-Content-Type-Options: nosniff
X-Server-Response-Time: 901
Content-Type: application/json
Accept-Encoding: identity,gzip
Date: Thu, 21 Apr 2022 01:25:01 GMT
Server: envoy
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Robots-Tag: noindex, nofollow, noimageindex
Content-Encoding: gzip
Vary: Accept-Encoding
X-Dropbox-Response-Origin: far_remote
X-Dropbox-Request-Id: 12cee658f5604167905348fd834c35d5
Transfer-Encoding: chunked

name: 'swiss.png'
path_lower: '/swiss.png'
path_display: '/swiss.png'
id: 'id:B71uxiCfSp4AAAAAAAAAOQ'
client_modified: '2022-04-21T01:25:00Z'
server_modified: '2022-04-21T01:25:01Z'
rev: '015dd1ffa916ba20000000266082110'
size: 215
is_downloadable: 1
content_hash: 'e87f106dcb11834c94b28b84ac739413b24390fae01127db49b81dcad29c62ae'

[Greg-DB]

The Dropbox API will save whatever data you supply in the HTTPS request body for the upload call as the file data, so you'll need to make sure you're sending the exact correct binary data that you want to store.

In the code you shared here, that seems to be your "data" variable. Make sure that variable contains the data you expect to be sending.

We can't officially provide support for third party platforms like MATLAB, as that's not made by Dropbox, but looking at the rest of your code, I recommend investigating the use of the fopen, fread, and char methods. For instance, is that char method call needed/correct? It looks like it may be modifying the data you mean to send.