How-tos.md

@@ -285,6 +285,7 @@ The region of interest of your tracking is specified by your mask. To get starte
 ```matlab
 %%% Create custom mask based on camera image
 dataRaw = load('arenaScreenshot.mat');	% black tape to mark boundaries of arena
+% figure; image(dataRaw.data);          % to visualize
 data    = dataRaw.data < 35;            % identify black pixels within image (manually adjust threshold)
 dataMargin = bwareaopen(data,20);       % remove unconnected pixel
 dataROI    = imfill(dataMargin,'holes');      % fill space within hexagon with 'true'