Specifies the type of ISIS callback being registered.
Values:
| IG_SCANCB_BEFORE_PAGE | Specifies the callback function called before page transfer is initiated. |
| IG_SCANCB_AFTER_PAGE | Specifies the callback function called when page transfer is completed. |
| IG_SCANCB_AFTER_DOC | Specifies the callback function called when all document pages transfer is completed. |
| IG_SCANCB_CAP_SET_5 | This value has been deprecated. It will be removed in the next version of ImageGear. |
| IG_SCANCB_AFTER_PAGE_UI | This value has been deprecated. It will be removed in the next version of ImageGear. |