Microsoft OCR unpredictable


Microsoft OCR is behaving unpredictably. During a live demo the workflow failed with the below error. After the demo when I tried it worked fine. This was in version 2016.2.6344.

Error {“message”:“Act on TasksError performing OCR: MicrosoftInternalError\r\n\r\nServer stack trace: \r\n at UiPath.Vision.OCR.OCRClient.ScrapeUsingHostService(OCRInput input, OCROptions options, CancellationToken cancelToken)\r\n at UiPath.Vision.OCR.OCRClient.Scrape(OCRInput input, OCROptions options, CancellationToken cancelToken, Boolean useHostProcess)\r\n at UiPath.Vision.UiImage.ScrapeOCR(OCROptions options, CancellationToken cancellationToken)\r\n at UiPath.Core.Activities.OCREngineActivity.<>c__DisplayClass36_0.b__0()\r\n at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)\r\n at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink)\r\n\r\nException rethrown at [0]: \r\n at UiPath.Core.Activities.ScopeActivity.OnFaulted(NativeActivityFaultContext faultContext, Exception propagatedException, ActivityInstance propagatedFrom)\r\n at System.Activities.Runtime.FaultCallbackWrapper.Invoke(NativeActivityFaultContext faultContext, Exception propagatedException, ActivityInstance propagatedFrom)\r\n at System.Activities.Runtime.FaultCallbackWrapper.FaultWorkItem.Execute(ActivityExecutor executor, BookmarkManager bookmarkManager)”,“level”:“Error”



Do you normally develop it using a Monitor and was the demo presented from your laptop to a projector or TV? If the display changed when you presented the demo, then it could be a resolution difference, maybe? I’m not that familiar with that error but from my experience if the OCR’s scale is set wrong it can throw an error. You might need a dynamic scale that starts large and decreases as an error is thrown.

Just throwing out ideas.


Hi Clayton, Thanks for responding. The Studio and Robot are deployed in a VM which we access via RDP. It opens a web page using a browser installed in the VM and tries to read a text in the webpage using OCR. So I guess the change of resolution in the laptop should not have affected OCR.


From what I see, RDP’ing from a laptop display environment will change the resolution than what you would use with a Monitor screen unless you manually select the display option before you Remote in, since it chooses the resolution that fits your laptop display. So that could still possibly be the case.



Hi Clayton, yes that seems to be the issue. I changed the display resolution to various levels and was able to simulate the issue. Thanks for quick tip.