Pinterest is fastest growing social photo sharing site around the world. Pinterest having default feature as you can share your Pinterest images to Facebook and Twitter. Google Plus is not in the list, So before you cannot share Pinterest images directly on Google Plus.
Now here is the cool Pinterest+ Chrome extension to bring google plus share buttons on Pinterest. allows you to +1 or Share your favorite pins to your Google+ Circles.
So here after users can share photos on Google+ Directly from Pinterest.
Link - Pinterest+