title: How to create a bitmap from another bitmap
body: <p>Let´s say I have a bitmap with 3 colors: red, green and blue (not mixed)</p>
  
  <p>What if I wanted to make a bitmap of the red part of the first bitmap?</p>
  
  <p>I´d like to take the red pixels from first bitmap (and its positions), and make another bitmap.</p>
  
  <p>Is that possible?</p>