title: How to send a png file by 'application/octet-stream' in Dart/Flutter to Microsoft Custom Vision?
body: <p>I know this question could be redundant, but I am trying to send a png file through a POST request to Microsoft Custom Vision in Flutter.
  This is my code:</p>
  <pre><code>void _makeRequest (File file) async {
      String url = &quot;&lt;url&gt;&quot;;
  
      Map&lt;String, String&gt; headers = {
        &quot;Content-Type&quot;: &quot;application/octet-stream&quot;,
        &quot;Prediction-Key&quot;: &quot;&lt;key&gt;&quot;,
      };         
  
      var bytes = file.readAsBytesSync();
           
      var response = await http.post(
        url,
        headers: headers,
        body: bytes,
      );
  
      print(response.body);
      print(response.statusCode);
    }
  </code></pre>
  <p>And when I run this code I get this response:</p>
  <pre><code>{&quot;code&quot;:&quot;ErrorUnknown&quot;,&quot;message&quot;:&quot;The request entity's media type 'appliction/octet-stream' is not supported for this resource.&quot;}
  </code></pre>