Image analysis – Image compression or coding – Parallel coding architecture
Reexamination Certificate
1994-11-30
2001-04-10
Au, Amelia (Department: 2623)
Image analysis
Image compression or coding
Parallel coding architecture
C382S239000
Reexamination Certificate
active
06215904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image compression. More particularly, the present invention relates to an apparatus and method for optimally compressing image data containing pictorial and text images.
2. Description of the Related Art
Conventional scanners provide digital data representing images from black/white and color documents, for example. Such digital data is then stored in memory; this digital data may be gray (e.g., 8 bits/pixel for black/white data or 24 bits/pixel for color data) or binary. Because considerable memory may be required to store such data, data encoders are often used to compress the data before it is stored, thereby conserving valuable memory. The compressed data is subsequently decompressed to produce the scanned image.
Although numerous different encoding schemes are available, each has deficiencies in encoding image data. Encoding schemes which use gray data as input can be set-up to be “lossy,” (e.g., having high compression ratios), resulting in some image degradation due to data loss. That is, gray image data compressed and decompressed using lossy encoding schemes cannot be fully recovered; while these gray data encoding schemes work reasonably well for continuous tone image data, typically containing low contrast images, they are not effective for text/line graphic gray image data, typically containing high contrast images. Similarly, encoding schemes which use binary data as input and are set up to be “lossless,” are effective for text/line graphics image data but are poor for halftone image data.
Also, different encoding schemes may be desirable in compressing different image data types, such as pictorial (continuous tone or halftone) or text. However, once a data encoder employing a particular encoding scheme is selected, the data encoder encodes the image data without regard for the image data type. Because documents may contain both pictorial (continuous tone or halftone) and text (character and line graphics) images, compressing image data representing a scanned document using a single encoding scheme may provide undesirable results. Thus, it is also desirable to optimally compress image data according to the different image data types.
SUMMARY OF INVENTION
Accordingly, the present invention is directed to an image encoding apparatus and method that substantially solves one or more of the problems due to limitations and disadvantages of the related art.
One advantage of the invention is compression and storing of image data with minimal image degradation as when printed on printers with different characteristics.
Another advantage of the invention is reduced memory requirements for storage of compressed image data without significant image degradation.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention includes an image compression apparatus comprising means for detecting image characteristics of image data, first means for encoding the image data in accordance with a first encoding scheme, second means for encoding the image data in accordance with a second encoding scheme, means for selectively storing encoded image data from one of the first and second encoding means in accordance with the detected image characteristics.
In another aspect, the invention includes a method of data compression, comprising the steps of receiving image data; detecting image characteristics in the received image data; compressing the received image data using a first compressor; compressing the received image data using a second compressor; selecting compressed image data from one of the first and second compressors based upon detected image characteristics; and storing the selected image data in memory.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 3496543 (1970-02-01), Greenly
patent: 5204756 (1993-04-01), Chevion et al.
patent: 5270837 (1993-12-01), Chen et al.
patent: 5276531 (1994-01-01), Chen et al.
patent: 5293430 (1994-03-01), Shiau et al.
patent: 5327262 (1994-07-01), Williams
patent: 5339172 (1994-08-01), Robinson
patent: 5392362 (1995-02-01), Kimura et al.
patent: 5517327 (1996-05-01), Nakatani et al.
Au Amelia
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Johnson Timothy M.
Xerox Corporation
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