Image analysis – Pattern recognition – Feature extraction
Reexamination Certificate
1998-11-25
2002-06-25
Mehta, Bhavesh (Department: 2621)
Image analysis
Pattern recognition
Feature extraction
C382S200000, C382S201000, C382S258000, C382S257000
Reexamination Certificate
active
06411733
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus for processing images having different object types. More particularly, the invention is directed to a method implemented in a system for separating character-type objects, stroke-type objects and large bitmap (or blob) type objects in a binary document image. The invention makes use of contour tracing techniques, statistical analysis of contour features, thinning techniques and image morphology.
While the invention is particularly directed to the art of image processing and object separation, and will thus be described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
Document images are fundamentally comprised of different colored picture elements (pixels). However, most of the known useful computational tools for accessing, transmitting, editing, displaying, and working with textual or semantic content require that image objects be represented in symbolic form.
In this regard, different symbolic representations exist for different types of image objects. For example, ASCII characters are useful for representing English text. Typically, text is converted to the ASCII character representation via Optical Character Recognition. In addition, chain-codes have been used successfully for representing curvilinear lines and unanalyzed bitmaps provide a satisfactory mechanism for representing complex or large objects or regions for which no shape model is given.
Certain software packages used for image processing, including the programs used with electronic interactive display boards such as the Tivoli/Meetingboard electronic whiteboard, maintain a data type for each of these types of image objects. When using such a program at an electronic interactive display board or workstation, stroke type objects are entered by freehand sketching, while character objects are entered by typing at the keyboard. Performing online OCR on pen input may also be possible. Currently, data can also be imported from bitmap images such as that obtained from a scanned image of a physical document, but these are treated only as unanalyzed bitmaps. The character and stroke data on them are not converted to editable character objects and stroke objects. This presents a difficulty if the objects require editing.
Some known methods for image processing simply classify connected components of an input bitmap. Others only apply image morphology operations to the input bitmap.
The present invention provides a new and improved image processing run method for separating object types which overcomes the above noted problems and difficulties and others. The method may be applied to any process where object type separation and editing is desired.
SUMMARY OF THE INVENTION
A method and apparatus for separating types of objects present in an image are provided. In one aspect of the invention, a method comprises the steps of inputting the image having objects including character type objects, stroke type objects and blob type objects, generating a first bitmap representing the image, determining which of the objects of the image are of the character type by comparing predetermined decision criteria to data obtained from the first bitmap, separating character type objects from the first bitmap to obtain a second bitmap, having only characters represented therein, and a third bitmap, and separating stroke type objects and blob type objects of the image, respectively, by selectively using techniques of thinning, dilation, and bitwise logical operations on at least one of the first and third bitmaps.
In another aspect of the invention, the method comprises performing N−1 thinning steps on the third bitmap to obtain a fourth bitmap, copying the fourth bitmap to obtain a fifth bitmap, performing another thinning step on the fourth bitmap, removing all non-interior pixels of the fifth bitmap to obtain a sixth bitmap, performing an image morphology based dilation on the sixth bitmap to restore pixels eroded by the thinning and removing steps and obtain a seventh bitmap, performing a bitwise boolean operation between the first bitmap and the seventh bitmap to obtain an eighth bitmap having only blob type objects represented therein, performing a bitwise boolean operation between the fourth bitmap and the eighth bitmap to obtain a ninth bitmap, and performing a tracing operation on the ninth bitmap to obtain a tenth bitmap having only stroke type objects represented therein.
In another aspect of the invention, the method further comprises obtaining a character type representation based on the second bitmap.
In another aspect of the invention, the method further comprises obtaining a blob type representation based on the eighth bitmap.
In another aspect of the invention, the method further comprises obtaining a stroke type representation based on the tenth bitmap.
In another aspect of the invention, a system is provided to implement the method.
Further scope of the applicability of the present invention will become apparent from the detailed description provided below. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.
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Bayat Ali
Fay Sharpe Fagan Minnich & McKee LLP
Mehta Bhavesh
Xerox Corporation
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