It tags 'suspects' it can't identify and provides what it 'thinks' is the closest match. The application then tries to identify words using character proximity. It can use word information to modify probable suspect identities. The suspects remain tagged for operator verification. Finally, the software will try to reconstruct the original page layout.
Accuracy decreases as quality declines.
Small type faces and decorative fonts can also pose recognition problems. OCR applications vary greatly in their ability to reproduce page layout, and few do well with anything more complex than a two column spread. Multi-column documents often use smaller type sizes, which also adversely affects ocr accuracy. OPC conducted a small informal test of four ocr packages before selecting Caere Corporation's OmniPage Pro version 8.0. It was consistently more accurate than the others tested, and did a better job of page layout recognition than most.