11. Next with your new channel still active, click the small button with a circle inside of it entitled ‘load channel as selection’. You can find this at the bottom of your channels palette left of the ‘create new channel’ button used before in step 5.

12. Now with your selection still active, go back to your layers palette and create a new layer. Fill it with black (or whatever color you want). Here is what I got as a final result.

13. And my layers palette looks like this. You can delete your ‘original’ cactus layer if you want.