Image analysis – Image compression or coding – Shape – icon – or feature-based compression
Reexamination Certificate
2001-01-03
2003-12-16
Lee, Cheukfan (Department: 2622)
Image analysis
Image compression or coding
Shape, icon, or feature-based compression
C382S233000
Reexamination Certificate
active
06665445
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a data structure for image transmission, an image coding method, an image decoding method, an image coding apparatus, an image decoding apparatus, a data storage medium which contains a program for implementing an image decoding process, and a data storage medium which contains a coded image signal.
More particularly, the invention relates to a data structure for image transmission that makes coded image signals decodable by decoding processes corresponding to a single coding method, which coded image signals have different data structures obtained by coding digital image signals corresponding to different schemes. Further, the invention relates to an image coding method and an image coding apparatus for generating a coded image signal having the above-described data structure for image transmission, and an image decoding method and an image decoding apparatus for decoding a coded image signal having the data structure for image transmission.
Furthermore, the invention relates to a data storage medium containing a program for implementing the decoding process according to the above-described image decoding method, and a data storage medium containing a coded image signal having the above-described data structure for image transmission.
BACKGROUND OF THE INVENTION
In order to store or transmit digital image information with high efficiency, it is necessary to compressively code the digital image information. As a typical method for compressive coding of digital image information, there is DCT (Discrete Cosine Transformation) represented by JPEG (Joint Photographic Experts Group) and MPEG (Moving Picture Experts Group). Besides, there are waveform coding methods such as sub-band coding, wavelet coding, and fractal coding.
Further, in order to eliminate redundant image information between display images, such as adjacent frames, inter-frame prediction using motion compensation is carried out. That is, a pixel value of a pixel in the present frame is expressed using a difference between this pixel value and a pixel value of a pixel in the previous frame, and this difference signal is subjected to waveform coding.
To be specific, an arithmetic encoder
10
a
as shown in FIG.
22
(
a
) is employed for coding a binary image signal S
2
which represents a display image of binary information and is obtained from a scanner of a facsimile machine or the like. For decoding a coded binary signal E
2
, an arithmetic decoder
10
b
is employed as shown in FIG.
22
(
b
). The arithmetic encoder
10
a
encodes the binary image signal S
2
by an arithmetic coding process which is used when transmitting a facsimile signal, such as MMR (Modified Modified Reed) or JBIG (Joint Bi-level Image Coding Experts Group), thereby generates a coded binary signal E
2
. The arithmetic decoding apparatus
10
b
decodes the coded binary signal E
2
by an arithmetic decoding process corresponding to the arithmetic coding process, thereby regenerates a decoded binary signal D
2
.
As shown in FIG.
22
(
c
), a coded binary signal
600
a
(E
2
) corresponding to one display image includes a synchronous signal
601
at the beginning, a header
603
that follows signal
601
, and shape data
604
that follows the header
603
.
Further, an image coding apparatus
20
shown in FIG.
23
(
a
) is employed for coding a digital image signal St treated in MPEG2, and an image decoding apparatus
25
shown in FIG.
23
(
b
) is employed for decoding a coded image signal Et. The digital image signal St treated in MPEG2 is a rectangle image signal which includes a luminance signal and a color difference signal for color display (gradation display), and information showing the horizontal and vertical size of an image on one display image (one frame). The image coding apparatus
20
comprises an information source encoder
20
a
which subjects the digital image signal (rectangle image signal) St to information source coding, and a variable-length encoder
20
b
which subjects the output from the encoder
20
a
to variable-length coding to generate a coded image signal (coded pixel value signal) Et. The image decoding apparatus
25
comprises a variable-length decoder
25
b
which subjects the coded image signal Et to variable-length decoding, and an information source decoder
25
a
which subjects the output from the decoder
25
b
to information source decoding to generate a decoded image signal (decoded pixel value signal) Dt.
The information source encoder
20
a
comprises a DCT processor
21
which subjects each of plural blocks, into which a display image (one frame) is divided, to DCT (Discrete Cosine Transform), and a quantizer
22
which quantizes the output from the DCT processor
21
. The information source decoder
25
a
comprises an inverse quantizer
26
which inversely quantizes the output from the variable-length decoder
25
b
, and an IDCT processor
27
which subjects the output from the decoder
25
b
to inverse DCT. As shown in FIG.
23
(
c
), a coded image signal
700
a
(Et) corresponding to one display image includes a 32-bit synchronous signal
701
at the beginning, a header
703
that follows signal
701
, and coded pixel value bit streams (coded texture bit streams)
71
C
1
,
71
C
2
,
71
C
3
, . . . corresponding to blocks C
1
, C
2
, C
3
, . . . , into which the display image is divided, respectively. The coded texture bit streams
71
C
1
,
71
C
2
, and
71
C
3
include 5-bit quantization scales
704
,
707
, and
710
, variable-length texture motion vectors (MV)
705
,
708
, and
711
, and variable-length texture DCT coefficients
706
,
709
, and
712
, respectively.
In recent years, a method for compressively coding and transmitting an image signal in the basis of individual object has been put to practical use. More specifically, an image, corresponding to one display image and composed of plural objects, is subjected to compressive coding and transmission in an object-wise manner, thereby increases the data compression ratio and enables decoding/reproducing of the objects separately. In this method, on the reproduction end, coded image signals corresponding to the respective objects are decoded and reproduced, and the reproduced image signals are synthesized to display an image corresponding to one display image. This object-by-object coding enables the user to freely combine images of objects to be displayed, whereby editing of a moving picture is facilitated. Furthermore, in this method, it is possible to display a moving picture without reproducing images of relatively unimportant objects, according to the congestion of the transmission line, the performance of reproduction apparatus, and the preference of the viewer. In other words, scalability in object units, i.e., to change the contraction scale of image display for each object, is realized.
In the object-by-object compressive coding of an image signal, since the respective objects have different shapes, an image signal of an arbitrary shape image (hereinafter, referred to as an arbitrary shape image signal) is subjected to compressive coding. The arbitrary shape image signal includes a texture signal (pixel value signal) for color display of an object (gradation display) and comprising a luminance signal and a color difference signal, and a shape signal representing the shape of an image. The shape signal indicates whether each pixel as a component of a display region is located outside the object or inside the object, and it is expressed by binary digit.
Further, there is a case where the arbitrary shape image signal includes transparency information representing the transparency of an object when the object is placed as a foreground image on a background image, in addition to the texture signal and the shape signal. The transparency information is usually expressed by a multivalued transparent signal of at least three bits. A combination of the binary shape signal (binary transparency signal) and the multivalued transparency signal is called a transparency signal. The multivalued
Lee Cheukfan
Parkhurst & Wendel L.L.P.
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