title: MATLAB: How would I convert an image array to a black and white array based on the colors?
body: <p>I have an image in matlab read in from a movie file. The image is a 3d array. How would I go through that image and if the colors are mostly red(eg. red>200 blue&lt;50 green&lt;50)
  make that part of the image black and ther other areas white?</p>
  
  <p>Eventually I would like to do this for the whole video, but I need to understand this first!</p>