Faxed document image restoration method based on local pixel patterns

Teruo Akiyama; Nobuo Miyamoto; Masami Oguro; Kenji Ogura

doi:10.1117/12.304637

1 April 1998 Faxed document image restoration method based on local pixel patterns

Teruo Akiyama, Nobuo Miyamoto, Masami Oguro, Kenji Ogura

Proceedings Volume 3305, Document Recognition V; (1998) https://doi.org/10.1117/12.304637
Event: Photonics West '98 Electronic Imaging, 1998, San Jose, CA, United States

Abstract

A method for restoring degraded faxed document images using the patterns of pixels that construct small areas in a document is proposed. The method effectively restores faxed images that contain the halftone textures and/or density salt-and-pepper noise that degrade OCR system performance. The halftone image restoration process, white-centered 3 X 3 pixels, in which black-and-white pixels alternate, are identified first using the distribution of the pixel values as halftone textures, and then the white center pixels are inverted to black. To remove high-density salt- and-pepper noise, it is assumed that the degradation is caused by ill-balanced bias and inappropriate thresholding of the sensor output which results in the addition of random noise. Restored image can be estimated using an approximation that uses the inverse operation of the assumed original process. In order to process degraded faxed images, the algorithms mentioned above are combined. An experiment is conducted using 24 especially poor quality examples selected from data sets that exemplify what practical fax- based OCR systems cannot handle. The maximum recovery rate in terms of mean square error was 98.8 percent.

Citation Download Citation

Teruo Akiyama, Nobuo Miyamoto, Masami Oguro, and Kenji Ogura "Faxed document image restoration method based on local pixel patterns", Proc. SPIE 3305, Document Recognition V, (1 April 1998); https://doi.org/10.1117/12.304637

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