Using GIMP: Correcting and Touching Up Your Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 111

Click the Scan button to activate the actual scan process.
Once the image is read, GIMP will open a new document for the scanned
image. Close the scan program, and don't forget to save the new image.
Exercise : Try to scan an image from within GIMP, following the given
procedures.
2.5.3 Editing a Scanned Image
To help you practice the editing steps that follow, you'll find an image called
miami.tif in the SampleImages folder on the accompanying DVD. Open the
file (choose File > Open in GIMP's Toolbox) and save it as miami-impro in an
exercise folder on your hard disk. Save the image in a high-quality file format,
such as XCF or TIFF.
After you open the file, you may notice a few defects. The image tilts to
the right because it wasn't inserted properly in the scanner.
In addition, the borders of the image jut out because it wasn't properly
cut, so it needs to be cropped.
The image also suffers from the moiré effect caused by an interference of
the print screen with the scanner screen. This particular image was captured
from a newspaper; this type of moiré effect does not occur in scanned
photographs.
Figure 2.40
GIMP's image window displaying
the miami.tif image. (Photo by
Claudius Seidl)