1. A method of processing a three-dimensional (“3D”) image, the method comprising: receiving a source image; receiving a 3D image depth selection value from a user; calculating shift values for shifting the received source image based on the received 3D image depth selection value; and applying the calculated shift values to the source image signal to generate a 3D depth-adjusted image, wherein calculating the shift values of the gray-scales for the reference view comprises: calculating a maximum shift value to a maximum gray-scale for the reference view based on the received 3D image depth selection value; calculating a minimum shift value to a minimum gray-scale for the reference view using the calculated maximum shift value; and calculating middle shift values to middle gray-scales for the reference view using the calculated maximum and minimum shift values and the middle gray-scales between the maximum gray-scale and the minimum gray-scale for the reference view, wherein the steps of receiving the source image, receiving the 3D image depth selection value, calculating the shift value, and applying the calculated shift value are performed using one or more circuits.