Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
1996-11-19
2001-07-24
Chang, Jon (Department: 2623)
Image analysis
Image compression or coding
Adaptive coding
C358S451000, C382S237000
Reexamination Certificate
active
06266449
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for processing information, and more particularly, to a method and apparatus for encoding image data.
2. Description of the Related Art
In a data encoding technique widely used to encode digital monochrome binary image data, image data is encoded raster by raster. For example, in MH, MR, and MMR techniques used in facsimiles, variable-length encoding is employed, in which image data is encoded on the basis of the length of succession of either white or black pixels (run length).
A fixed-length encoding technique is also used. One technique of the fixed-length encoding is vector quantization in which an image data is divided into blocks and a fixed-length code is assigned to each block. In this technique, encoding is performed with a constant compression ratio. However, the information quality of coded data differs from block to block and thus the quality of decoded data or the quality of a reproduced image varies from block to block.
In image communication devices such as a facsimile device, a reversible encoding algorithm is usually employed so that a decoding device can reproduce an image identical to the original image. In some cases, an irreversible coding algorithm is also employed so as to achieve a higher compression ratio although a certain degree of degradation occurs in a reproduced image.
As described above, in variable-length encoding, the amount of generated codes varies depending on the image, and thus the disadvantage of this technique is that it is difficult to encode the data with a compression ratio no greater than a particular desired value (and thus it is difficult to encode the data with a particular memory capacity).
On the other hand, in fixed-length encoding, although it is possible to maintain the compression ratio at a desired value, there is a problem that local degradation occurs in the quality of decoded data.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus for coding image data with a compression ratio no greater than a desired value, beyond which there could be produced significant degradation in the quality of the image due to the encoding/decoding process.
To achieve the above object, the present invention in one aspect thereof provides an information processing apparatus including: monitoring means for monitoring the amount of codes associated with image data which has previously been encoded; and encoding means for encoding image data to be encoded using either a reversible encoding algorithm or an irreversible encoding algorithm selected depending on the amount of codes associated with the previously encoded image data.
Another object of the present invention is to provide an apparatus for coding color image data with a desired compression ratio without producing significant degradation in the quality of the image due to the encoding process.
To achieve the above object, the present invention in another aspect provides an information processing apparatus including: monitoring means for monitoring the amount of encoded color image data which has already been generated; selection means for selecting an encoding algorithm from a plurality of encoding algorithms having various compression ratios, the selection of the encoding algorithm being performed on the basis of the amount of generated codes; and encoding means for encoding the color image data to be encoded in accordance with the selected encoding algorithm, wherein the encoding means encodes a plurality of components constituting the data representing the color image, and the compression ratio is changed by changing the compression ratio associated with each component constituting the color image.
Still another object of the present invention is to prevent a visible difference in the image quality among large areas.
To achieve the above object, the present invention in still another aspect provides an information processing apparatus including: monitoring means for monitoring the amount of codes associated with an image which has already been encoded; selection means for selecting whether a pixel to be encoded is encoded in the form of an M-level pixel or in the form of an N-level pixel, said selection being performed on the basis of said amount of codes, where N≠M; and encoding means for encoding the block of image to be encoded on the basis of the selection result given by said selection means.
A further object of the present invention is to provide an apparatus for decoding data in a manner which allows the data to be encoded in an improved efficiency.
To achieve the above object, the present invention in another aspect provides an information processing apparatus capable of decoding first encoded data which has been encoded using a first encoding algorithm and also capable of decoding second encoded data which has been encoded using a second encoding algorithm different from the first encoding algorithm, the apparatus comprising: monitoring means for monitoring the amount of codes associated with first data to be decoded which has been input prior to second data to be decoded; and decoding means for decoding the second data to be decoded selectively using a first decoding algorithm corresponding to the first encoding algorithm or a second decoding algorithm corresponding to the second encoding algorithm, the selection of the decoding algorithm being performed on the basis of the monitoring result of the monitoring means.
Furthermore, it is another object of the present invention to provide an image forming apparatus which can achieve any of the above objects and which has the capability of converting the image data described in a printing language such as the PDL (Page Description Language) into the format which can be dealt with by a printer and supplied the resultant data to the printer.
To achieve the above object, the present invention in another aspect provides an image forming apparatus including: input means for inputting image data described in a page description language; storage means for converting the input image data into a different format and storing the resultant image data in a predetermined memory; monitoring means for monitoring the amount of codes associated with image data which has previously been encoded and which is stored in the storage means; encoding means for encoding the image data to be encoded selectively using one of a reversible encoding algorithm and an irreversible encoding algorithm, the selection of the encoding algorithm being performed on the basis of the amount of codes associated with the previously encoded image data; decoding means for decoding the encoded image data to be decoded selectively using a decoding algorithm corresponding to one of the reversible decoding algorithm and the irreversible decoding algorithm; and output means for outputting the decoded image data to a printer.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in conjunction with the accompanying drawings.
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Canon Kabushiki Kaisha
Chang Jon
Fitzpatrick ,Cella, Harper & Scinto
Johnson Timothy M.
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