As I was working on my digital exhibit and archive, I began to wonder about what I would do if one of my images was too large to scan. Would I have to take a digital picture of it? Should I scan it in two parts and post both? During our scanning practicum, I posed this question to Melitte Buchman, the Digital Manager at NYU. She is an expert in digital preservation and other digital imaging skills. She revealed that the answer is literally “stitching” the two images together. This blog post presents itself as a little tutorial in how to stitch an image together, whether it is an over sized poster of an event in Greenwich Village, a map of the neighborhood, or a panorama of a building in Greenwich village. All you is a scanner, your image(s), Photoshop, a steady hand, and some patience.
First, we scan the image. (A quick note: although this blog post will not go into how preservation scanning works, if you are preservation scanning, make sure the scanner you are using is color calibrated and clean. If you are scanning a photograph, wear gloves. ) I am scanning a mock-up of a poster created by the Nicaragua Solidarity Network, which is a left action group working out of 339 Lafayette Street in Greenwich Village. They were most active in the late 1980s and early 1990s, as the Sandinista government was going out of power. The poster is oddly shaped, and does not fit in the scanner.
First scan the entirety of the top of the image, as much as can fit in the scanner. Once done, shift the image, scanning the other end of the image. Do NOT just scan the portion that remained outside of the scanner on the first pass. We want to have as much overlap as possible, so scan as much of the bottom as can fit in the scanner.
After both sides of the image are scanned, it is time to open up your scanned images in Photoshop. Most computers come with Photoshop Elements, which is sufficient for this project. Make sure that you create a new version of your scanned images and rename it, for both preservation purposes and just in case you make a mistake that you can’t undo and need to start from scratch.
First paste in the top half of your image. We need a canvas to work on, so to make the background larger, first go to Image–>Re-size–>Canvas Size. Here, we not only increase the length of the image by changing the height percentage (200 or 250 is more than enough, changing the width is also helpful, by making the width of the image 110 percent larger, you get a better sense of the edges of the images), we also shift the image up so as to give us room on the bottom of the canvas to move the second half around. I like making the background black so as to really see where the edges are.
Now, it is time to add the second half of the image. Make sure it is added as a second layer. Move and nudge the image around until it is overlapping. I matched up “T” and “H” in the “THE” as close as possible. Sometimes rotating the second layer will also line up the images better.
Once the two images are lined up as close as possible, notice the seam in between the two halves of the image. This needs to be removed. By using the polygonal lasso tool, we are able to cut out the seam, little by little, until the bottom half comes through and the seam is invisible. This is where having a lot of overlap comes in handy. The lasso creates a custom selection around a section on the image. Dragging the lasso through black parts of the image or natural seams (folds in the paper, straight lines) are all good places to create cut out lines. This part can be time consuming and require patience and a delicate hand, but done well, it can look like one full image.
Once the seam is cut out, it is time to put the two layers together. Under Layers, click on “Flatten Image.” Then crop the image to the appropriate size and then you are done!
As great a skill as stitching is, it still should only be used for presentation and access. Manipulating digital images deteriorates the image by taking away pixels, and makes it unstable for future migrations to new formats. Use with caution and have fun using digital tools!