diff --git a/src/gui/__init__.py b/src/gui/__init__.py
--- a/src/gui/__init__.py
+++ b/src/gui/__init__.py
@@ -1,12 +1,15 @@
 import threading
+import logging as log
 import tkinter as tk
 from PIL import ImageTk
 import PIL
 
 import config
+from epoint import EPoint
 from corners import Corners
 import image_analyzer
 from go import Go
+from grid import Grid
 
 
 class MainWindow(tk.Frame):
@@ -15,23 +18,31 @@ class MainWindow(tk.Frame):
 		self.corners=Corners()
 
 		self.currentFrame=None
-		self.boardGrid=None
+		self._boardGrid=None
 		self.gameState=None
 
 		self.img=None
+		self._imgSizeCoef=1
+		self._imgShift=EPoint(0,0)
 
 		tk.Frame.__init__(self, master)
 		self.grid(column=0,row=0)
 		self._createWidgets()
 
-	def setCurrentFrame(self,frame,grid):
+	def setCurrentFrame(self,frame):
 		self.currentFrame=frame
-		self.boardGrid=grid
 
 		w=int(self.imgView['width'])
 		h=int(self.imgView['height'])
 		self.img=ImageTk.PhotoImage(frame.resize((w,h),resample=PIL.Image.BILINEAR))
 
+		wo,ho=self.currentFrame.size # o for original
+		widthRatio=wo/w
+		heightRatio=ho/h
+		self._imgSizeCoef=max(widthRatio,heightRatio)
+		# shift compensates possible horizontal or vertical empty margins from unmatching aspect ratios
+		self._imgShift=EPoint(wo-w*self._imgSizeCoef,ho-h*self._imgSizeCoef)/2
+
 	def setGameState(self,gameState):
 		pass
 
@@ -67,7 +78,11 @@ class MainWindow(tk.Frame):
 	def addCorner(self,x,y):
 		self.corners.add(x,y)
 		if self.corners.canonizeOrder():
-			self.parent.sendMsg("setCorners",(self.corners,))
+			# transform corners from show coordinates to real coordinates
+			log.debug(self.corners.corners)
+			self._boardGrid=Grid(self.corners.corners)
+			corners=[(c*self._imgSizeCoef+self._imgShift) for c in self.corners.corners]
+			self.parent.sendMsg("setCorners",(corners,))
 		# 	self.boardGrid=Grid(self.corners)
 		# 	self.boardView.setBoardGrid(self.boardGrid)
 		#
@@ -78,30 +93,23 @@ class MainWindow(tk.Frame):
 		if self.currentFrame and self.img:
 			self.imgView.create_image(2,2,anchor="nw",image=self.img)
 
-			origWidth,origHeight=self.currentFrame.size
-			widthRatio=origWidth/self.img.width()
-			heightRatio=origHeight/self.img.height()
-			sizeCoef=max(widthRatio,heightRatio)
-
-			# shift=EPoint(origWidth-self.img.width()*sizeCoef,origHeight-self.img.height()*sizeCoef)/2
-
 		for corner in self.corners.corners:
 			self.markPoint(corner.x,corner.y)
 
-		if self.boardGrid!=None and config.gui.showGrid:
+		if self._boardGrid!=None and config.gui.showGrid:
 			for r in range(19):
-				a=self.boardGrid.intersections[r][0]
-				b=self.boardGrid.intersections[r][-1]
+				a=self._boardGrid.intersections[r][0]
+				b=self._boardGrid.intersections[r][-1]
 				self.imgView.create_line(a.x,a.y,b.x,b.y,fill='#00ff00')
 			for c in range(19):
-				a=self.boardGrid.intersections[0][c]
-				b=self.boardGrid.intersections[-1][c]
+				a=self._boardGrid.intersections[0][c]
+				b=self._boardGrid.intersections[-1][c]
 				self.imgView.create_line(a.x,a.y,b.x,b.y,fill='#00ff00')
 
-		if self.boardGrid!=None and config.gui.showBigPoints:
+		if self._boardGrid!=None and config.gui.showBigPoints:
 			for r in range(19):
 				for c in range(19):
-					((r1,c1),(r2,c2))=image_analyzer.relevantRect(self.boardGrid.intersections[r][c],*(self.boardGrid.stoneSizeAt(r,c,sizeCoef)))
+					((r1,c1),(r2,c2))=image_analyzer.relevantRect(self._boardGrid.intersections[r][c], *(self._boardGrid.stoneSizeAt(r, c)))
 					self.imgView.create_rectangle(r1,c1,r2,c2,outline="#00ffff")
 
 		self.imgView.grid()
@@ -121,7 +129,6 @@ class MainWindow(tk.Frame):
 class BoardView(tk.Canvas):
 	def __init__(self, master=None):
 		# self.detector=ImageAnalyzer()
-		self.boardGrid=None
 
 		tk.Canvas.__init__(self, master)
 		self.configure(width=360,height=360,background="#ffcc00")
@@ -210,17 +217,17 @@ class GUI:
 			msg=incomingQueue.get()
 			if incomingQueue.empty():
 				incomingEvent.clear()
-			print(msg)
+			log.info(msg)
 			self._handleEvent(msg)
 
 	def _handleEvent(self,e):
-		actions={"setCurrentFrame": self._frameHandler}
+		actions={"setCurrentFrame":self._frameHandler}
 		(actionName,args,kwargs)=e
 
 		return actions[actionName](*args,**kwargs)
 
-	def _frameHandler(self,newFrame,grid):
-		self.mainWindow.setCurrentFrame(newFrame,grid)
+	def _frameHandler(self,newFrame):
+		self.mainWindow.setCurrentFrame(newFrame)
 		self.root.event_generate("<<redrawImgView>>")
 
 	def _stateHandler(self,e):