title: Negative RGB Values
body: <p>How do I visualize negative RGB values?.<br>
  As per OpenCV Documentation:<br>
  CV_8S - 8-bit signed integers ( -128..127 )<br>
  Does it mean that -128 mean 0 and 127 means 255? <br>
  If yes, then why do we need to have <br>
  CV_8U - 8-bit unsigned integers ( 0..255 )?<br>
  I am sorry if my question is trivial.<br></p>