The need to center something on page is so common, you'd think design software would have a command for it. But most don't.
Sure, there's usually an Align palette or command hidden someplace, with a Center Align option, but that's for aligning two or more things you've created; not for aligning one thing with the page itself.
So, designers need to figure out a workaround. Most often, it's a two-step process: Create a horizontal and vertical guideline that intersect at the exact center of the page/artwork, then use that as a reference point to align the center points of objects.
To create objects that are centered on the page, holding down the Option/Alt key and dragging from that guideline intersection outwards will work in most programs.
To center existing objects, drag them by their center point (a non-printing handle that normally appears when the item is clicked on with the program's selection tool) to the guideline intersection. As long as Snap to Guides is turned on, the object will "snap" to the guide intersection.
The problem is, how do you create those centered guidelines? You could use the mathematical method — divide page width/height by 2 and place guides there — but that's a pain (math!) and not every program lets you set guides with such precision. And sometimes the initial width/height of what you want to center "to" isn't obvious, as is the case with the opaque pixels in a partially-transparent Photoshop layer.
InDesign's Create Guides command provides the fastest way to create the guides:
1. Go to ID's Layout menu and choose Create Guides
2. Enter 2 in the Rows field, 2 in the Columns field, and 0 for gutter width for both; then click OK. (Or just tab through the fields and type 2, 0, 2, 0, return.)
Result: One vertical and one horizontal guide that intersect at the exact center of the page (or centered relative to the margins, if that's the option you chose in Create Guides).
Alas, Illustrator lacks a Create Guides command. But like InDesign, one or more guidelines in Illustrator can be selected and acted upon with many palette and menu commands. And that's the key to centering the guides on the page (actually, "Artboard" in Illy-speak).
First, a little set-up: Make sure nothing is selected, then open the Align palette and from its fly-out menu, choose Align to Artboard. Also make sure that Lock Guides is turned off in View -> Guides.
1. Drag out one horizontal and one vertical guideline from the rulers (View -> Show Rulers if necessary) and drop them anywhere on the page.
2. With the selection tool, drag a small selection rectangle around the intersection of those guides to select them both. Or you could click one and shift-click the other one.
3. In the Align palette's first row of icons (Align Objects), click the second icon (Horizontal Align Center) and the fifth icon (Vertical Align Center). Bam, the guides center themselves on the page. You may want to turn Lock Guides back on at this point.
Interesting that the Align palette works with guides, isn't it? You can use the feature to create your own custom grids —- just drag out a bunch of guidelines, select them and use the Distribute icons to space them out.
You can't use a menu or palette to quickly place guides in Photoshop, nor can you select more than one at a time. But Photoshop has some subtle features that will help you center-snap a guideline you're dragging out from the ruler.
Make sure that Snap is turned on in Photoshop's View menu, and that "Guides" is one of the items that things will Snap to (in Snap's fly-out menu). Also, if you don't see Rulers, choose Show Rulers from the View menu.
To create guidelines that are centered relative to the entire image area:
1. Target a layer that is completely filled with pixels — that is, one where you can't see any checkerboard pattern indicating transparency. The default white-filled background layer, if you have one, will work. Otherwise, create a new layer just for this purpose and fill it with a color.
2. On that layer, drag out a guideline from one of the rulers. As you near the center of your image, you'll "feel" it snap to the center. Now do the same for the other ruler.
After you've created the 2 guides, you can delete any temporary layer you created. The guides remain and are "live" on any layer in your file.
You won't feel any magical snapping if you've targeted a partially-filled layer, but sometimes you need to find the center of its artwork, which could be quite different than the center of the overall image. No problem.
To create guidelines that are centered on a layer's opaque pixels:
1. Target the layer.
2. Choose Edit -> Free Transform (Command/Control-T), which puts a bounding box just around the layer's artwork — the checkerboard pattern representing "no pixels here" is ignored.
3. Drag out your guidelines. They'll snap to the edges and to the center of the bounding box.
4. When you're done placing guides, press the Escape key or click the Cancel Transform icon in the options bar to remove the bounding box.
Tiplets: Hold down the Shift key as you drag a guideline to have it Snap to ruler tick marks. Hold down the Control key to turn off any automatic guide snapping (even to Transform's bounding box) while you're dragging the guideline, allowing you to place it anywhere you like.
Argh. There's no easy, precise way to create centered guidelines in QuarkXPress without an XTension. All we can do is use the same method since Quark v3 … the mathematical method described above; or the "close enough" method:
1. With Snap to Guides turned on (View menu), drag out a picture box the width and height of the area of you want to center things to. (Snap to Guides is useful if the box you're creating needs to snap to the margin guides.)
2. Zoom in as close as you can to the intersection of the "X" in the empty picture box.
3. Drag out a vertical and a horizontal guideline from the rulers and drop them on top of the intersection of the X.
4. Zoom out and delete the picture box. Your guidelines now intersect at the center of whatever area the picture box defined.