steps:
-setup a 1680x1050 screen
-transform any image so that it is 1400 height & portrait mode (so width is lower than 1400)
example: some of my test images were : 800x1400 , 933x1400 ...
-view this image in fullscreen (the image should not be in real size)
-a white line appears at the bottom
here's what it looks like with a random transformed image once displayed by xnviewmp 0.48:

PS: the background color is normal