diff --git a/src/gui.py b/src/gui.py
--- a/src/gui.py
+++ b/src/gui.py
@@ -33,7 +33,16 @@ class Application(tk.Frame):
     # board with detected stones
     self.boardView=BoardView(self)
     self.boardView.grid(column=1,row=0)
-    
+
+    # more controls below the board
+    self.scaleTresB=tk.Scale(self, orient=tk.HORIZONTAL, length=200, from_=0.0, to=100.0, command=lambda x: self.redrawImgView())
+    self.scaleTresW=tk.Scale(self, orient=tk.HORIZONTAL, length=200, from_=0.0, to=100.0, command=lambda x: self.redrawImgView())
+    self.scaleTresB.set(30.0)
+    self.scaleTresW.set(60.0)
+    self.scaleTresB.grid(column=0,row=1,columnspan=2)
+    self.scaleTresW.grid(column=0,row=2,columnspan=2)
+
+    # render everything
     self.redrawImgView()
   
   ## Stores a grid corner located at x,y coordinates.
@@ -67,10 +76,12 @@ class Application(tk.Frame):
     widthRatio=origWidth/self.img.width()
     heightRatio=origHeight/self.img.height()
     sizeCoef=max(widthRatio,heightRatio)
+    tresB=self.scaleTresB.get()
+    tresW=self.scaleTresW.get()
     
     shift=EPoint(origWidth-self.img.width()*sizeCoef,origHeight-self.img.height()*sizeCoef)/2
     
-    self.boardView.redrawState(self.imgOrig,sizeCoef,shift)
+    self.boardView.redrawState(self.imgOrig,sizeCoef,shift,tresB,tresW)
     
   ## Marks a point at the image with a green cross. Used for corners.
   def markPoint(self,x,y):
@@ -92,9 +103,13 @@ class BoardView(tk.Canvas):
     self.drawGrid()
     
     self.grid()
-    
-  def redrawState(self,img,sizeCoef,shift):
-    self.detector.analyze(img,30,65,sizeCoef,shift)
+
+  ## Redraws and reananalyzes the board view.
+  #
+  # @param tresB upper intensity treshold for a pixel to be considered black, [0-100]
+  # @param tresW lower intensity treshold for a pixel to be considered white, [0-100]
+  def redrawState(self,img,sizeCoef,shift,tresB,tresW):
+    self.detector.analyze(img,tresB,tresW,sizeCoef,shift)
     
     for r,row in enumerate(self.detector.board):
       for c,point in enumerate(row):