You can add a grid to your photo in an image editing program when you want to be able to place text or other graphics in exact locations. In programs that support layers, you can create a grid that you can easily toggle on and off to print. Microsoft Office products allow you to create a non-printing grid that you can use to align images and text.
Adding Non-Printing Guides
In Photoshop and Photoshop Elements, you can use the program's built-in grid to display a non-printing grid over your photo. You can customize the color of the grid, change it from solid lines to dots or dashes, adjust its size and even add subdivisions. In Photoshop, access grids by going to the "View" menu, then "Show," and selecting "Grid." To change grid settings, go to "Edit," click on "Preferences" and select "Guides, Grid and Slices." GIMP, an image-editing program available for Linux, Mac and Windows computers, has a default grid for every image that you can toggle on an off. The default grid looks like black crosshairs, but it can be changed to squares. GIMP's built-in grid cannot be printed.
Adding Guides That Will Print
Programs that support layers will let you add a grid to your image, while giving you the flexibility of printing or not printing the gridlines. In order to be able to print guidelines, you'll need to create them yourself. Create a separate layer in your image file. In Photoshop, select "Window" from the menu and click "Layers" to open this palette. Click the icon at the top right and select "New Layer" and click "OK." Draw your grid on this layer using the pen or pencil tool. You can customize the color and width of your grid lines and use Photoshop's built-in ruler to line them up. To print the guidelines, make sure your grid layer is above your image layer and that the eye icon shows.