Adapted to openCV 4.1 + holes count + Quit button

Author: AbsurdePhoton

README.md

@@ -128,16 +128,16 @@ Basic operations:
   * you can change the grid color with the control under the grid layer button
   * use the zoom controls on the right to zoom in / out - you can also use the mouse wheel over the viewport
   * click on the thumbnail to position the zoomed area in the viewport
-  * hold the middle mouse button on the viewport, or hold down the < SPACE > key to move the view position with your mouse when the image is zoomed in - you can also use the scrollbars
+  * hold the middle mouse button on the viewport, or hold down the "SPACE" key to move the view position with your mouse when the image is zoomed in - you can also use the scrollbars
 
 * Modifiy the cells:
   * the superpixel algorithms often misses important details: you can define your own cells with the special "Create new cell" button
   * the editor enters a special state: you have to draw your cell in white color
   * you can set pixels with the left mouse button, and unset them with the right
-  * use the <CTRL> key to floodfill entire zones, just like explained before
+  * use the "CTRL" key to floodfill entire zones, just like explained before
   * once a pixel is set, it can become the origin of a line:
     * hold down the "X" key and move the mouse over the viewport: a temporary line appears
-    * release <X> and the line is set
+    * release "X" and the line is set
     * the end of a line becomes the new origin from which you can draw another one
     * click with the left mouse button to set a pixel to change once again the origin of the lines
   * you can only UNDO the last action like before