Photoshop - How to apply gradient to only part of an image in photoshop


I am trying to create a wallpaper with a white background, and a kind of floating picture/portrait of Robert Heinlein. I have the picture edited down to the parts I want, but its not white, so I want to apply a surrounding gradient to the image (see below) so that it fades, all around, into the white wallpaper background. Whenever I try to do this however, I can only manage to apply the gradient to the entire image--Is there a way to apply it only to the parts of the image I want? i.e. start at pure white at the edge, and then fade, but only to a certain point into the existing photo?


7/14/2015 3:50:00 AM