OCR image preprocessing method for image enhancement of scanned documents by reversing invert text

• US 5,579,414 A
• Filed: 05/22/1995
• Issued: 11/26/1996
• Est. Priority Date: 10/19/1992
• Status: Expired due to Term

• Current Assignee: Accusoft Corporation
• Original Assignee: TMSSequoia Co.
• Inventors: Allen, Dana R., Fast, Bruce B.
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): Tran, Phuoc
• Application Number:
  US08/447,095
• Time in Patent Office: 554 Days
• Field of Search: 382/254, 382/274, 382/275, 382/245, 382/286, 358/261.1, 358/447, 358/448, 358/453, 358/462, 358/447
• US Class Current: 382/254
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/1478 of characters or characters lines
• CPC Class Codes: G06V 30/155 Removing patterns interfering with the pattern to be recognised, such as ruled lines or underlines
• CPC Class Codes: G06V 30/164 Noise filtering
• CPC Class Codes: H04N 1/38 Circuits or arrangements for blanking or otherwise eliminating unwanted parts of pictures H04N1/387 takes precedence
• CPC Class Codes: H04N 1/3878 Skew detection or correction
• CPC Class Codes: H04N 1/409 Edge or detail enhancement; Noise or error suppression

Abstract

In a run-length represented image an image area with reverse print is recognized. Two borders (left and right) are determined and in a plurality of steps the run transitions are removed, first on the left border of the area and then at the right border of the area, causing all runs within the area of reverse print to take on the reverse color.

Claims

1. A scanned document run-length coded image enhancement process for reversing image sections of reverse printed textual matter contained in said run-length coded image, each of said image sections having a left and a right border, and having a black background color and a white foreground color, said process including the steps for

determining one of said image sections containing reverse print information

and subdividing said image section into an upper section and a lower section,

reversing scan line wise said background color and said foreground color at the left border of said upper and lower section,

reversing scan line wise said background color and said foreground color at the right border of said image section;

said reversing of background and foreground color including summation of run-length segments left and right of a border in one run-length segment with the color assignment of the run-length segment on the left side of said border.