title: Reproduce zathura's recolor function
body: <p>is it possible to programmatically reproduce zathura's recolor function?
  I would like to write a program that takes a pdf file as an input and spits out a pdf file with zathura's &quot;recolor&quot; transformation.</p>
  <p>I've searched but am not aware of existing code /software that does the same thing.</p>
  <p>related links:
  <a href="https://git.pwmt.org/pwmt/zathura" rel="nofollow noreferrer">https://git.pwmt.org/pwmt/zathura</a></p>