Xerox copiers 'alter numbers' on documents

Some Xerox copiers have an Image compression problem Scans made by some models of Xerox copiers are altering numbers on documents, a German computer scientist has discovered .
The problem as been blamed on faults with image compression software used in certain settings offered by the models in question, the Xerox Workcenter 7535 and 7556.
Image compression is a method of reducing the size of files.
The image compression in the Xerox copiers, Jbig2, substitutes figures it thinks are the same, researcher David Kriesel said, meaning similar numbers were being wrongly interchanged.
Kriesel said scans he made of some construction plans had altered room dimensions, as the number 6 would be turned into an 8 and vice versa, with other numbers being affected too.
The problem is not due to errors with optical character recognition algorithms, Kriesel wrote in a blog, but "is a lot worse - patches of the pixel data are randomly replaced in a very subtle and dangerous way."
"The scanned images look correct at first glance, even though numbers may actually be incorrect."
Scanning modes with the quality level set to "High" or "Higher" do not present the problem, Xerox said in a statement. Only the "normal" quality level uses Jbig2 compression, the company said.
If the lower quality option is picked, Xerox noted, the following disclaimer is displayed: "The normal quality option produces small file sizes by using advanced compression techniques. Image quality is generally acceptable, however, text quality degradation and character substitution errors may occur with some originals."
Source: UPI