title: Understanding color matrix of hue
body: <p>This is a color matrix in ARGB:</p>
  
  <pre><code>[
  
  R,0,0,0,0,
  
  0,G,0,0,0,
  
  0,0,B,0,0,
  
  0,0,0,A,0,
  
  0,0,0,0,1
  
  ]
  </code></pre>
  
  <p>And I know its hue color matrix below:
  (
  refers to gskinner's source code:
  <a href="http://gskinner.com/blog/archives/2007/12/colormatrix_cla.html" rel="nofollow">http://gskinner.com/blog/archives/2007/12/colormatrix_cla.html</a>
  )<br/></p>
  
  <pre><code>define lr=0.213
  define lg=0.715
  define lb=0.072
  define a=0.143
  define b=0.140
  define c=-0.283
  define hueangle
  define cos=cos(hueangle)
  define sin=sin(hueangle)
  </code></pre>
  
  <hr>
  
  <pre><code>[
  
  lr+cos*(1-lr)+sin*(-lr),lg+cos*(-lg) +sin*(-lg),lb+cos(-lb) +sin*(1-lb),0,0,
  
  lr+cos*(-lr)+ sin*(a),lg+cos*(1-lg)+sin*(b),lb+cos(-lb) +sin*(c),0,0,
  
  lr+cos*(-lr)+ sin*(-(1-lr)),lg+cos*(-lg) +sin*(lg) ,lb+cos(1-lb)+sin*(lb),0,0,
  
  0,0,0,1,0,
  
  0,0,0,0,1
  
  ]
  </code></pre>
  
  <hr>
  
  <p>(Thanks son_of_fire for pointing out the inexplicitness of the questions in the last edition.)</p>
  
  <p><em><strong>Question</em></strong></p>
  
  <ul>
  <li>What formulas led to this hue matrix especially the numbers a,b and c in it?</li>
  </ul>