These are before and after samples of a Retouching job for a professional portrait photographer:

The main job here was to move the fellow on the extreme left two places to the right (to fill in the gaping hole between the third and fourth man.) The client also wanted the image to be more nearly square. There were several challenges to be overcome:
a) The photographer used a wide angle lens (probably because he didn't have enough space to maneuver), and he shot the group not head on, but at an angle. Consequently the people on the left were closer to the camera and thus, appeared larger than the others on the right (see before, top.) This is very disturbing in photographs of people. Also the entire room exhibited a strong perspective distortion.
b) In order for proportions to remain the same, the bearded man had to be precisely shrunk when moved so he didn't appear unnaturally large. (Also, his hands had to be eliminated.)
c) After this step the perspective distortion had to be lessened by shrinking the image vertically more toward the left than toward the right, in a graduated manner. This meant that the image was now a rhombus, with the smaller side on the left:

In order to cure this, extra image material had to be "created" on the left, both on top and on the bottom; also, mirror material had to be created when the man was moved. Notice how now everyone is about the same size, as if shot head on. (See after, bottom.)