title: How to create data fom image like "Letter Image Recognition Dataset" from UCI
body: <p>I am using letter_regcog example from OpenCV, it used dataset from UCI which have structure like this:</p>
  
  <pre>
  Attribute Information:
       1. lettr   capital letter  (26 values from A to Z)
       2. x-box   horizontal position of box  (integer)
       3. y-box   vertical position of box    (integer)
       4. width   width of box            (integer)
       5. high    height of box           (integer)
       6. onpix   total # on pixels       (integer)
       7. x-bar   mean x of on pixels in box  (integer)
       8. y-bar   mean y of on pixels in box  (integer)
       9. x2bar   mean x variance         (integer)
      10. y2bar   mean y variance         (integer)
      11. xybar   mean x y correlation        (integer)
      12. x2ybr   mean of x * x * y       (integer)
      13. xy2br   mean of x * y * y       (integer)
      14. x-ege   mean edge count left to right   (integer)
      15. xegvy   correlation of x-ege with y (integer)
      16. y-ege   mean edge count bottom to top   (integer)
      17. yegvx   correlation of y-ege with x (integer)
  </pre>
  
  <p>example:</p>
  
  <pre>
  T,2,8,3,5,1,8,13,0,6,6,10,8,0,8,0,8
  I,5,12,3,7,2,10,5,5,4,13,3,9,2,8,4,10
  </pre>
  
  <p>now I have segmented image of letter and want to transform it into data like this to put recognize it but I don't understand the mean of all value like "6. onpix   total # on pixels" what is it mean ? Can you please explain the mean of these value. thanks.</p>