When annotating empty fields in Azure, you can specify the bounding box by drawing a rectangle around the field. You can select the field by clicking and dragging your mouse to create the bounding box. You can label the field by assigning a label to the bounding box you created. If you cannot select the empty field, you may need to change the settings or the image preprocessing steps to make the field more visible.
Here are a few resources to help you annotate empty fields in Azure:
- Documentation for Azure Form Recognizer
- Annotation guidelines for Azure Form Recognizer
- Azure Cognitive Services - Form Recognizer: Quickstart (C#)
These resources explain how to use Azure Form Recognizer and annotate fields for form recognition.