title: ebay api error Uploaded picture has unsupported file format
body: <p>I am trying to upload an image as a binary MIME attachment to ebays api UploadSiteHostedPictures.  I keep receiving the following error: Uploaded picture has an unsupported file format.  The image is a jpg but i have tried png, and that didn't work either.</p>
  
  <p>I have gone through the ebay knowledgebase java and c# examples and i cannot understand where i am going wrong.</p>
  
  <p>Here is where i am passing the image file.</p>
  
  <pre><code>List&lt;int&gt; imageBytes = imageFile.readAsBytesSync();
  String base64Image = base64Encode(imageBytes);
  </code></pre>
  
  <p>Header</p>
  
  <pre><code>Map&lt;String, String&gt; uploadPictureHeader = {'X-EBAY-API-CALL-NAME': 'UploadSiteHostedPictures', 'X-EBAY-API-SITEID': '0', 'X-EBAY-API-RESPONSE-ENCODING': 'XML', 
                                                'X-EBAY-API-COMPATIBILITY-LEVEL': '967', 'X-EBAY-API-DETAIL-LEVEL': '0', 'Cache-Control': 'no-cache', 
                                                'Content-Type': 'multipart/form-data; boundary=FormBoundary7MA4YWxkTrZu0gW'};
  </code></pre>
  
  <p>Body</p>
  
  <pre><code>String requestUploadedSiteHostedPicture = '''--FormBoundary7MA4YWxkTrZu0gW
                                                      Content-Disposition: form-data; name="XML Payload"
  
                                                      &lt;?xml version="1.0" encoding="utf-8"?&gt;
                                                      &lt;UploadSiteHostedPicturesRequest xmlns="urn:ebay:apis:eBLBaseComponents"&gt;
                                                          &lt;RequesterCredentials&gt;
                                                              &lt;eBayAuthToken &gt;$userTokenOAuth&lt;/eBayAuthToken&gt;
                                                          &lt;/RequesterCredentials&gt;
                                                          &lt;PictureName&gt;Vase&lt;/PictureName&gt;
                                                          &lt;PictureSet&gt;Standard&lt;/PictureSet&gt;
                                                          &lt;ExtensionInDays&gt;20&lt;/ExtensionInDays&gt;
                                                      &lt;/UploadSiteHostedPicturesRequest&gt;
  
                                                      --FormBoundary7MA4YWxkTrZu0gW
                                                      Content-Disposition: form-data; name="Vase"; filename="Vase.jpg"
                                                      Content-Transfer-Encoding: base64
  
                                                      $base64Image
  
                                                      --FormBoundary7MA4YWxkTrZu0gW--''';
  </code></pre>
  
  <p>Making the call</p>
  
  <pre><code>final response = await http.post(
        url,
        headers: uploadPictureHeader,
        body: requestUploadedSiteHostedPicture,
        encoding: Encoding.getByName("UTF-8")
      );
  </code></pre>
  
  <p>I have used online binary converters to convert the image as well, but that didn't work either.  Any help is much appreciated, thank you.</p>