I love the pattern/print.  It has very pretty and cheery shades of blues and greens. , reminds me of a watercolor painting.  They do help keep out the light.  Not completely​ dark, but with a shade behind the curtain, very effective.  If you're looking for complete darkness, you'll definitely​ need to add something.  In the pic (taken in full sun), the left handside has patio doors behaind, the right hand side​ is a window with​​ a shade pulled down.