diff --git a/src/gui/imgview.py b/src/gui/imgview.py
--- a/src/gui/imgview.py
+++ b/src/gui/imgview.py
@@ -66,7 +66,7 @@ class ImgView(ResizableCanvas):
 			log.debug(self._corners.corners)
 			self._boardGrid=Grid(self._corners.corners)
 			corners=[self._transformPoint(c) for c in self._corners.corners]
-			self._parent.sendMsg("setCorners",(corners,))
+			self._parent.detector.setCorners(corners)
 
 		self.redraw()
 
@@ -81,6 +81,9 @@ class ImgView(ResizableCanvas):
 	def setRecording(self):
 		self.bind('<1>',lambda e: None)
 
+	def isSet(self):
+		return self._img is not None
+
 	def _onResize(self,event):
 		w=self._width
 		super()._onResize(event)