But basically the JBIG2 image compression algorithm used in those scanners looked for certain repeating patterns, and incorrectly compressed certain portions of the image into “close enough” blocks of pixels. Unfortunately, that meant that scanned number data wasn’t guaranteed to be accurate, even when the decoded output clearly looked like a number with no distortion or noise.
He’s written up his findings in English, for anyone who prefers English over German or text over video.
But basically the JBIG2 image compression algorithm used in those scanners looked for certain repeating patterns, and incorrectly compressed certain portions of the image into “close enough” blocks of pixels. Unfortunately, that meant that scanned number data wasn’t guaranteed to be accurate, even when the decoded output clearly looked like a number with no distortion or noise.
It’s worth the full read.
You left out what I feel is the best part: even in the “uncompressed” mode, even when that was disabled, it was still happening sometimes.