Image analysis – Image segmentation – Distinguishing text from other regions
Reexamination Certificate
1999-04-15
2001-09-11
Johnson, Timothy M. (Department: 2623)
Image analysis
Image segmentation
Distinguishing text from other regions
C382S165000, C382S228000
Reexamination Certificate
active
06289122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to the use of machine intelligence to detect text on a composite document page that may also contain graphics and images. In particular, the invention relates to computer programs and systems for identifying text and non-text areas in documents.
2. Description of the Prior Art
Electronic image files of printed pages are relatively easy to obtain with the use of a computer and a scanner. A typical image processing system is described by Hisao Shirasawa et al., in U.S. Pat. No. 5,696,842, issued Dec. 9, 1997. Color documents that are scanned-in typically include images, graphics, and text components. A separator is used to divide M×N picture elements according to the type of image in each. Picture elements with black and while values are differentiated from those that are not all-black or all-white. Purpose of such image processing system is to allow for high degrees of image compression because the black and white image areas can be encoded with far fewer bits per pixel than a pixel for a color graphic.
Unfortunately, such prior art techniques are concerned with such issues as compression/decompression and not with specifically identifying the textual elements of the image. While optical character recognition (OCR) systems are known, these systems are not so much concerned with the fast and accurate reproduction of text in a printed page that also contains graphics as they are with the character identification, typically for an all text source.
It would be advantageous to provide an improved text detection technique in which image processing was performed based upon prior knowledge of the nature of the source image components, e.g. text or image, prior to commencing such processing.
SUMMARY OF THE INVENTION
The invention provides a technique for segmenting an image into text areas and non-text areas. The image is stored with the following information per pixel: gray scale intensity (4 bits) and an indication of whether the pixel is neutral or color (1 bit). In the preferred embodiment of the invention, the image, e.g. a scanned RGB image, is converted to 0-15 levels of intensity and has a neutral/color indication bit assigned to each pixel.
The technique proceeds in three phases as follows:
Tile the image by square blocks, e.g. 6×6 or 8×8 for 600 dpi images, and store information about each block in a buffer.
Sweep the buffer left to right three tile rows at a time and make a preliminary decision for every tile-block in the middle row.
Examine the decision made in the previous step in a context block, e.g. a 3×3 block, and make revisions if necessary.
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IBM Technical Disclosure Bulletin, 1988, No. 7, Armonk, New York.
Electronics For Imaging, Inc.
Glenn Michael A.
Johnson Timothy M.
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