Communications of the ACM
Xerox Scanners Found to Sometimes Alter Numbers
A Ph.D student has discovered that Xerox scanners can randomly alter numbers on documents when reproducing them, if a specific combination of image quality and compression settings are used. Xerox admits the issue exists, and suggests using a higher-quali
Credit: IDG News Service
University of Bonn Ph.D. student David Kriesel has found that Xerox scanners sometimes randomly alter numbers on documents when reproducing them if a specific combination of image quality and compression settings are used.
Xerox acknowledges the problem and is advising customers to use a higher-quality scanner setting to avoid the problem.
When an image is scanned in TIFF mode, a pixel-for-pixel reproduction, the copy was identical to the original. However, when Kriesel used the image-compression feature, the numbers started getting mixed up. There appears to be a correlation between the font size and the scan's resolution.
Kriesel was able to narrow the problem down to the way the scanner's JBIG2 image compression works. To reduce file space, the compression system looks for areas of an image that are similar and, when it finds them, makes one compressed version and reuses it across all the similar areas. Kriesel says the problem apparently only exists when using the scanner's normal, lowest-quality setting, which is the only one that uses JBIG2 compression. He notes that Xerox says the scanner's "high" and "higher" settings use a different compression system.
From IDG News Service
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