Another tip....I read in an earlier post in another thread where someone said that it was difficult to align two halves of a picture when you had to scan one half, then scan the second half and join them together, like a centerfold. With Photoshop, it's not hard at all to join the two halves.
First, scan the two halves of the picture that you are going to join together. Remember to scan the first half of the picture, then rotate the second half of the picture 180 degrees and scan that. In my example, I used a centerfold, but you need to do the same thing even if the two halves are on different pages and not connected together like the centerfold is. (see image 1)
In the first picture, you can see the two halves of the picture, and they are turned 180 degrees from each other. Now rotate one of them 180 degrees so that they are facing the same direction, then select the Measure Tool from the toolbar. If you don't see the Measure Tool, it's in the flyout menu of the eyedropper. Just click and hold on the eyedropper and you will see the Measure Tool. (see image 2)
To use the measure tool, locate the line that runs down the centerfold where it was folded. You don't need to see the whole line, just part of it. You might need to zoom in to see it. Okay, now place the Measure Tool somewhere along the line, click and hold the Measure Tool at that spot to anchor it, then drag it along the line to a place further long the line, then let go of the Measure tool. This will create a highlighted line along the center line of the picture.(see image 3)
Now, go to Image-Rotate Canvas and click on Arbitrary. In the window that pops up, you will see that the angle and direction are already selected. This is what the Measure tool does. Just click Ok and the picture will rotate the exact amount you need to make it straight.
Now do the same thing to the other half. You will now have the two halves perfectly aligned so that you can stitch them.
