1. Convert to Grayscale
 2. Open Curves
 3. Select the black line with the eye dropper for reference
 4. Play with those points until you are satisfied.

[![enter image description here][1]][1]

5. Open levels again and fine tune it with more control.

[![enter image description here][2]][2]



[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/BS2uA.gif
  [2]: https://i.sstatic.net/5ZSj8.gif
  [3]: https://i.sstatic.net/iQDGU.png