Sometimes an image in a magazine stretches across two or more pages (with a fold-out poster, it could be up to 9 pages). Editing them back into a seamless image is something of a pain, but here are some tips.
For this example, we're going to use a two-page spread from a glue-bound magazine, since that's more of a challenge than a stapled mag. First of all, this is what a glue-bound page looks like when removed using heat:
All of those holes on the right side of the image are where the page is glued to the spine. The page has not been torn - those small pieces of the page simply aren't there to begin with (or rather, were removed during the binding process). This is as perfectly complete as you can possibly get when debinding a glue-bound mag. All of those holes are going to have to be filled in during editing. But this method of debinding is absolutely necessary if you want a seamless join.
Suppose you had saved a few minutes and debound this magazine with a paper cutter, slicing away the spine and gutter. This would be the result:
Looks fine, right? Yes, it looks perfectly good, and the small loss of image on the far right might be acceptable if this was a single-page image. But if you try to join two pages that have been similarly debound using a paper cutter, you can see that the image is not going to look seamless at all:
Fixing the image at this point is pretty much impossible, since there is simply too much information missing (indeed, an actual paper slicer is almost definitely going to crop off even more than I did for this example picture). Because of course, this is actually what the two pages look like side by side after being debound with a slicer:
ALL of that space in the center needs to be filled in order for the picture to look good. Suddenly those tiny holes from a heat-debound mag don't look so bad, eh?
When joining images in Photoshop, you will be extremely reliant upon a handy feature called the "content-aware fill tool."
First, you'll want to fill in all of those holes on the gutter side of each page. Sometimes this is very easy. If a page has nothing but solid color or very simple shapes with straight lines extending to the edge, you can usually just select the length of the gutter side with a rectangle tool, use the content-aware fill tool, and presto - you're done. This is what you will do with most pages which don't actually have images reaching all the way into the gutter.
When joining images across multiple pages however, using the rectangle tool across the length of the page when selecting the area to be filled will make the image harder to match up with the facing page since it will alter all of the space between the holes as well. Look at the following pair of pictures carefully and you'll see that the image on the right isn't quite what it should be after having the selected rectangular area filled in:
The answer, of course, is to use the lasso tool to select each hole individually, and using the content-aware fill on those holes only, leaving as much of the original image as possible intact.
The next step is to line up the pictures as closely as possible. They will almost never align perfectly, so you will likely end up with some empty space at the top or bottom of one of the pages that will need to be filled, again, using the content-aware fill tool:
Next comes detail work, using the fill tool (or sometimes the clone stamp) to more seamlessly blend areas that don't quite match up:
Often times, the angle of one page will be slightly different that that of the other. Getting them both to align perfectly is almost impossible, so another trick worth experimenting with, particularly when it comes to straight lines that don't quite line up from one page to the next, is the warp tool:
(After warping the image, you'll want to use the fill tool or possibly clone stamp to fix the warped pattern of the color dots in the background).
And finally, when you've got your image joined to your satisfaction, simply select one half of it (one page), cut and paste it into a separate window, apply any level adjustments, and save. Then with the remaining half, crop the area where the second page was by zooming way in to make sure you get the crop pixel perfect so that the pages will look seamless when viewed in two-page mode in a CBR reader:
(select one page)
(cut it away and paste it in a different window)
(Zoom in to crop)
Be sure to use the exact same level adjustments on both pages. You could do this before splitting the images apart, or course, but it's likely that you'll have already created an action set that will adjust levels, resize and save your image all with a single button press, in which case, you'll want to wait until the images have been split before performing the action.
Voilà!! Now you see why editing can take so damn long if done well!