Preprocessing of dot-matrix/ink-jet printed text for Optical Cha

Details Preprocessing of dot-matrix/ink-jet printed text for Optical Cha Preprocessing of dot-matrix/ink-jet printed text for Optical Cha

1992-01-21

1993-05-18

Boudreau, Leo H.

Image analysis

Histogram processing

For setting a threshold

382 18, 382 54, G06K 938

Patent

active

052127419

ABSTRACT:
Method and apparatus are disclosed for processing image data of dot-matrix/ink-jet printed text to perform Optical Character Recognition (OCR) of such image data. In the method and apparatus, the image data is viewed for detecting if dot-matrix/ink-jet printed text is present. Any detected dot-matrix/ink-jet produced text is then pre-processed by determining the image characteristic thereof by forming a histogram of pixel density values in the image data. A 2-D spatial averaging operation as a second pre-processing step smooths the dots of the characters into strokes and reduces the dynamic range of the image data. The resultant spatially averaged image data is then contrast stretched in a third pre-processing step to darken dark regions of the image data and lighten light regions of the image data. Edge enhancement is then applied to the contrast stretched image data in a fourth pre-processing step to bring out higher frequency line details. The edge enhanced image data is then binarized and applied to a dot-matrix/ink jet neural network classifier for recognizing characters in the binarized image data from a predetermined set of symbols prior to OCR.

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