Trouble loading large PNG in PI


I am trying get some panoramic PNG images to load in the pi. The images will then scroll across the screen from right to left. The images load when the width matches the screen (1920 x 648), but do not load when it exceeds the width of the screen. I have changed the GPU Memory to 256, as suggested in other forums, but it still uploads blank if it is any larger than the resolution noted above.