Use the x key to zoom in and the z key to zoom out, or use the plus and minus buttons or the slider to zoom in and out. Use the arrow keys or drag to pan through the image. If you want to reset zoom and position press r.
This project is made by splitting up a 1920*1440 image in a grid of 4x4 smaller 480*360 images so 16 images. I did it online with a spllitting tool: https://www.split-pix.org/. That works because 1920/4=480 and is 1440/4=360. Using clones you can then make the images smaller and putting the grid of images back together. So then because you have all 480*360 image parts displayed at the same time it looks like HD image. Then i also programmed that the tiles that are outside of the view hide so that they dont stay there at the edges.