Usage:
    osca.py xxx.jpg xxx2.jpg xxx3.jpg
    
Keys:
    's'         Save the selected object to the picture's object list
    'S'         Save the picture and its object list to the (picture-object list) dictionary
    'Ctrl + s'  Save the (picture-object list) dictionary to file
    'r'         Clear the picture's object list
    '->'        Move to next picture in the picture list
    '<-'        Move to previous picture in the picture list
    'Esc'       Stop processing current image, will move to next picture in the picture list
    'q'         Quit the process
    
Mouse:
    Drag a Rect to select an object
    Move the your mouse close to the border of the Rect and drag to adjust the size of the Rect
    Click anywhere else to cancel the selection
    
The result file is set in preference.txt