Analyze tab
     
    This tab is accessible only while in image mode. It is used to control the 
    quality analysis process :
      
        - The "x" an "y" numeric fields set the origin (in pixels unit) of the
	  analyze square (0,0 is at the bottom left corner).
 The square position can also be (and usually is) changed by dragging 
	  it in the image frame.
 Frame a detail on which the quality of the image can be judged,
	  or the entire planet if it lacks conspiscuous details.
- The "Size" button menu sets the analyze square side, it has the same
	  constraints as in the align tab.
	  
- The "Method" popup selects the analysis method to use,
	  entropy or power spectrum, cf. 
	  concepts.
	
- The "Analyze" button starts to analyze each image selected for 
	  processing (ie: with a checkmark).
 Once started, it is impossible to select another tab and the "Analyze"
	  button becomes a "Stop" button.
- The autoselect slider becomes enabled once the images quality has 
	  been analyzed. When you change the quality threshold, images with a 
	  quality lower than the threshold are desselected for futher processing,
	  or images with a quality higher than the threshold are selected.
      
When this tab is selected, the image frame displays the image of the 
      highlighted line in the list frame. The analyze square is drawn as a red 
      square on this image.
      The left and right arrow keys, delete, backspace, space and return keys 
      act as in the list tab.
    During analyze process, each analyzed image is :
      
	- highlighted in the list frame, 
	
- its estimated quality column updated,
	
- displayed in the image frame.
 This last feature can be disabled in user preferences, to speed up 
	  the analyze.
Stack tab ...