
Joshua S. answered 06/17/19
Experienced Graphic Designer + Illustrator with a BFA in Visual Comm.
Two ways come to mind to do this. One would be using the slice tool in Photoshop. You would probably want to set guides at the point where you want to "cut" the image, and then click the slice tool and select areas that you want to export separately. Be noted that I believe you'd need to export for web in order for this to take effect.
Another way, and I think probably a better way, would be to use Adobe Illustrator with Artboards set up with no gaps, so they touch each other. You'd want to do the math ahead of time. So if your image was 300px by 1600px, and you wanted to cut it into four separate images, you'd want to set up the file with four Artboards, each one 300px by 400px, and make sure that there is no gap between them. You can move these around in an already-existing document with the Artboard tool (which should be in the bottom left of your screen, in the toolbar. Then, you'd lay your image across all your Artboards, and export. If you're printing, make sure your resolution is set to 300.
Hope this helps!
Josh