Image object content generation device and padding device

Details Image object content generation device and padding device Image object content generation device and padding device

2001-10-24

2004-12-21

Brier, Jeffery A. (Department: 2672)

Computer graphics processing and selective visual display system

Computer graphics processing

Graphic manipulation

C345S611000, C345S640000, C348S580000, C348S597000

Reexamination Certificate

active

06833845

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an image object content generation device, and more specifically relates to a padding processing for padding outside of an image object.
(2) Description of the Prior Art
MPEG (Moving Picture Coding Experts Group)-4 has attracted attention as an image compression method suitable for a mobile terminal or Internet that has dramatically developed in these years, as well as being suitable for conventionally storing media or digital broadcasting. MPEG-4 is an object-based image coding method, and one of the important features thereof is to resolve an image signal into that of a background and that of a component part (an object), such as a figure and a building, so as to compress and extend the image data per object. As an application of this method, there are needs of enlarging and reducing a screen size, that is, the needs for displaying an image taken by a home video camera in a small-sized liquid crystal display panel, such as a mobile phone, for example. There are also needs of changing a size of image content data, such as a figure image, into an arbitrary size, that is, the needs for importing a figure image separately taken on a blue background into a pre-taken background so as to composite both.
FIG. 1A
is a diagram showing one block of N×N pixels (N is a positive integer number) including a boundary between an object and a background when an image including an object and a background is scanned in the direction of an arrow.
FIG. 1B
is a graph showing a change of a pixel value (a brightness value, for example) of an image signal when the image in the block as shown in
FIG. 1A
is scanned in the direction x. In these figures, a horizontal axis indicates a location in the direction x, and a vertical axis indicates a pixel value at that location. And pixel values of an object pixel and a background pixel are indicated as digital values showing a gray scale in the range of 0≦Y≦255. An enlarged boundary portion of an image actually taken by using a CCD (Charge Coupled Device) or the like is the image as shown in the right part of
FIG. 1A
, where an image signal of a background is mixed into an object portion or that of an object is mixed into a background portion. As a result, if a static image comprising an object and a background as shown in
FIG. 1A
is scanned in the direction of the arrow, the image signal in the object (0≦x<x0) is almost constant. On the contrary, the frequencies of the image signal become high around the boundary x0 between an object and a background, and they gradually turn to be constant the further they are from the boundary portion, as shown in FIG.
1
B.
If an image block cut out from a frame includes an object pixel and a background pixel as the block shown in the right part of
FIG. 1A
does, when image data is compressed per object as a unit in MPEG-4, the image signal of the block includes high frequency components as shown in FIG.
1
B and is not suitable for shape-adaptive discrete cosine transform (SA-DCT). Therefore, a padding processing needs to be performed in MPEG-4 for removing high frequency components of the image signal before performing the shape-adaptive discrete cosine transform. Padding processing is a processing for removing high frequency components by supplying an alternate pixel value to a background pixel adjacent to an object pixel (i.e., by padding a background pixel with an alternate pixel value).
As a prior art padding processing device, Japanese Laid-Open Patent Application H10-210470 Gazette discloses an example thereof, and this processing will be explained as follows based on FIG.
2
.
FIG. 2
is a block diagram showing a structure of a conventional padding processing device disclosed in Japanese Laid-Open Patent Application H10-210470 Gazette. The padding processing device comprises a boundary block detection unit
100
, a block scanning unit
210
, a block compensation unit
220
and SA-DCT unit
300
. The boundary block detection unit
100
scans plural image blocks of the same size of N×N pixels (N is a positive integer number) including an object pixel and a background pixel and detects a background pixel intervening between object pixels on the identical line or row in the image block (a padding pixel). The block scanning unit
210
calculates an alternate pixel value by using a pixel value of an object pixel. The block compensation unit
220
supplies the alternate pixel value to the padding pixel and generates a padded image block. Thereby, in the compensated object area, the padding pixel that is a background pixel intervening between object pixels is padded with the alternate pixel value, and as a result, high frequency components in the boundary portion are removed. In this way, by performing a padding processing in the block compensation unit
220
, the SA-DCT unit
300
can perform appropriate shape-adaptive discrete cosine transform of the input image signal of the object area and the background area including an object pixel and a background pixel, respectively.
However, since the conventional padding processing device just replaces a pixel value of a padding pixel with an alternate pixel value, there is a high possibility that quality of a generated image is deteriorated. Therefore, if a size of content image cut out from an input image is changed into a certain size, for example, it is difficult to generate it as high grade pixel data. Also, there are problems such that a larger memory capacity is required, a larger circuit scale is required, more electric power is consumed, and processing speed is reduced for realizing the padding processing without deteriorating the grade of the cutout object image.
SUMMARY OF THE INVENTION
It is accordingly a first object of the present invention, in the light of the above-mentioned conventional problems, to provide a padding device that can perform a padding processing without deteriorating a grade of an object image, and an image object content generation device that can generate high quality image object content by such a padding processing.
Also, the second object of the present invention is to provide a padding device and an image object content generation device that can be realized in a small circuit scale and perform high speed processing.
The above-mentioned first object may be achieved by an image object content generation device of the present invention that comprises: a key generation unit operable to generate a key that is a reference to distinguish an object pixel from a background pixel per pixel of an inputted image signal; a frame size changing unit operable to change a frame size of the image signal; a low frequency component passing unit operable to remove high frequency components of the image signal which was processed in the frame size changing unit; a pixel compensation unit operable to perform a padding processing, according to Low Pass Extrapolation padding algorithm, to the image signal which was processed in the low frequency component passing unit based on the key generated by the key generation unit; and a pixel selecting unit operable to select one of the image signal which was processed in the low frequency component passing unit and the image signal which was processed in the pixel compensation unit.
As described above, in the image object content generation device, the key generation unit generates a key that is a reference to distinguish an object pixel from a background pixel per pixel of an inputted image signal. The frame size changing unit changes a frame size of the image signal. The low frequency component passing unit removes high frequency components of the image signal which was processed in the frame size changing unit. The pixel compensation unit performs a padding processing to the image signal which was processed in the low frequency component passing unit by using Low Pass Extrapolation padding algorithm. The pixel selecting unit selects one of the image signal which was processed in the low frequency c

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