Computer graphics processing and selective visual display system – Computer graphics processing – Graphic manipulation
Reexamination Certificate
1999-02-01
2002-11-19
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Graphic manipulation
C345S582000
Reexamination Certificate
active
06483521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to image composition methods, image composition apparatuses, and data recording media and, more particularly, to a process of compositing an image having a shape with another image, and a recording medium which contains a program implementing the composition process by software.
BACKGROUND OF THE INVENTION
In recent years, we have greeted the age of multimedia in which audio, video and other data are integrally handled, and the conventional information media, i.e., means for transmitting information to men, such as newspapers, magazines, televisions, radios, and telephones, have been adopted as the objects of multimedia. Generally, “multimedia” means to represent, not only characters, but also diagrams, speeches, and especially images simultaneously in relation with each other. In order to handle the conventional information media as the objects of multimedia, it is necessary to transform the information of the media into a digital format.
When the data quantity of each information medium described above is estimated as a quantity of digital data, in case of characters, the data quantity for each character is 1~2 byte. However, in case of speech, the data quantity is 64 kbps (quality for telecommunication) and, in case of moving picture, it is more than 100 Mbps (quality for current television broadcasting). So, in the information media such as televisions, it is not practical to handle such massive data as it is in a digital format. For example, although visual telephones have already been put to practical use by ISDN (Integrated Services Digital Network) having a transmission rate of 64 kbps-1.5 Mbps, it is impossible to transmit an image of a television camera as it is by the ISDN.
So, data compression technologies are demanded. In case of visual telephones, a moving picture compression technology standardized as H.261 by (Tu-T (International Telecommunication Union-Telecommunication Sector) is employed. Further, according to a data compression technology of MPEG1, it is possible to record image data, together with audio data, in an ordinary music CD (compact disk).
MPEG (Moving Picture Experts Group) is an international standard of data compression for moving pictures. In MPEG1, data of a moving picture is compressed to 1.5 Mbps, i.e., data of a television signal is compressed to about {fraction (1/100)}. Since the transmission rate to which MPEG1 is directed is limited to about 1.5 Mbps, MPEG2 has been standardized to meet the demand for higher image quality. In MPEG2, data of a moving picture is compressed so that its transmission rate becomes 2~15 Mbps, to realize the quality for current television broadcasting.
Under the existing circumstances, standardization of MPEG4 is now proceeded by the working group for standardization of MPEG1 and MPEG2 (ISO/IEC JTC1/SC29/WG11). MPEG4 enables coding and handling of image information in object units, and thereby realizes new functions required in the age of multimedia.
One feature of MPEG4 is that a plurality of image signals for displaying different objects, for example, a foreground image (object)
102
and a background image (object)
100
shown in
FIG. 23
, are coded separately.
An image signal corresponding to each object is composed of a shape signal expressing the shape of the object, and a texture signal expressing the texture of the object. When coding the image signal, the shape signal and the texture signal are coded by different coding methods.
The texture signal is composed of a luminance signal indicating the brightness of the image of the object, and a chrominance signal indicating the color of the image of the object. The resolution of the chrominance signal is different from that of the luminance signal. To be specific, the size of one pixel as one of components of an image space obtained from the luminance signal (the area of one pixel on the display screen) is ¼ of the size of one pixel in an image space obtained from the chrominance signal. The luminance signal (chrominance signal) is composed of pixel values corresponding to the respective pixels in the image space.
The resolution of the shape signal is equal to the resolution of the luminance signal. To be specific, the size of one pixel as one of components of an image space obtained from the shape signal is equal to the size of one pixel as one of components of an image space obtained from the luminance signal. The shape signal is composed of pixel values corresponding to the respective pixels in the image space.
Accordingly, the luminance signal and the shape signal corresponding to a region enclosing one object on the screen (hereinafter, referred to as an object region) have the same number of pixel values.
In the following description, the image spaces obtained from the luminance signal, the chrominance signal, and the shape signal are referred to as a luminance space, a chrominance space, and a shape space, respectively; the pixels as components of the luminance space, the chrominance space, and the shape space are referred to as luminance pixels, chrominance pixels, and shape pixels, respectively; and the pixel values of the luminance pixels, the chrominance pixels, and the shape pixels are referred to as luminance data, chrominance data, and shape data, respectively. Further, a shape space, a luminance space, and a chrominance space obtained from an image signal (i.e., shape, luminance, and chrominance signals) corresponding to one object are equal in the reference position and the size.
When the pixel values of the shape signal are represented by either “0” or “non-0”, shape pixel whose pixel values is “0” is positioned outside the image of the object in the shape space, while a shape pixel whose pixel value is “non-0” is positioned inside the image of the object in the shape space.
On the other hand, decoding is performed as follows. As shown in
FIG. 23
, coded data (coded texture signal and coded shape signal) corresponding to the respective objects (foreground image and background image) are decoded, and the texture signals of the foreground image
100
and the background image
102
are composited by using the decoded shape signal to reproduce a composite image
106
. The
FIG. 23
, reference numeral
104
designates the shape of the object obtained from the shape signal. In this composition of texture signals, composition of luminance signals and composition of chrominance signals are carried out.
By the way, since the resolution of the chrominance signal is ¼ of the resolution of the luminance signal or the shape signal as described above, the decoded shape signal (hereinafter also referred to as an unconverted shape signal) cannot be used as it is for the composition of chrominance signals. So, the resolution of the shape signal must be converted to generate a shape signal adapted to the resolution of the chrominance signal (hereinafter also referred to as a converted shape signal).
As a method for converting the resolution of the shape signal, MPEG4 employs a method described in “MPEG4 Video Verification Model Ver8.0 (ISO/IEC JTC1/SC29/WG11 N1/96, pp. 17).
Since the resolution of the chrominance signal is ¼ of the resolution of the shape signal as described above, one pixel in the chrominance space corresponds to four pixels in the image space obtained from the uncovered shape signal. Further, since the resolution of the decoded shape signal is adapted to the resolution of the chrominance signal, one pixel in the chrominance space corresponds to one pixel in the image space obtained from the converted shape signal.
So, in the above-described resolution conversion method, when one of the four shape pixels corresponding to one chrominance pixel has the pixel value which is not “0”, in other words, when a shape pixel whose pixel value is “non-0” exists in the four shape pixels corresponding to one chrominance pixel, one shape pixel corresponding to the chrominance pixel in the image space obtained from the converted shape signal has the pixel value of “non-0”.
Herein
Boon Choong Seng
Kadono Shinya
Takahashi Jun
Burr & Brown
Luu Matthew
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