Image analysis – Image compression or coding – Polygonal approximation
Reexamination Certificate
1998-10-19
2002-04-16
Mehta, Bhavesh (Department: 2621)
Image analysis
Image compression or coding
Polygonal approximation
C382S243000, C345S441000
Reexamination Certificate
active
06373989
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an iterated image transformation and decoding apparatus and method, and a recording medium. More particularly, the present invention relates to an iterated image transformation and decoding apparatus and method which, by using iterated transformation, decodes a coded bit stream output from a coder for an image which is provided to a system which performs low-rate-coding of an image, or efficient transmission or storage of an image, and a recording medium.
2. Description of the Related Art
As a typical conventional image compression method, a commonly called JPEG (Joint Photographic Coding Experts Group) method standardized by the ISO is known. This JPEG method uses DCT (Discrete Cosine Transform), and when a relatively high bit rate is assigned, provides a satisfactory coded/decoded image. However, if the number of coding bits is reduced to some degree, block distortion which is characteristic of the DCT become conspicuous, and image degradation becomes noticeable.
In addition to this, recently, an image compression method using an iterated function system (IFS) is beginning to attract attention. This method utilizes self-similarity of an image under the precondition that when a part of an image is taken out from the entire image, another image which closely resembles the taken-out image is present in the form of a different size within the image. In this iterated function system, the block distortion such as that of the above-described JPEG is not conspicuous, and the self-similarity among the blocks of different sizes within the image is utilized, yielding the advantage that there is no dependence upon the resolution during decoding. This iterated transformation coding is also called fractal coding, and applications to various fields are expected.
The basic construction of the above-described iterated transformation coding is shown in, for example, “Image coding based on a fractal theory of Iterated Contractive Image Transformations” by Arnaud E. Jacquin, IEEE Transactions on Image Processing, Vol.1, No.1, pp.18-30. The iterated transformation and coding apparatus shown herein is shown in
FIG. 9
, and the iterated transformation and decoding apparatus shown herein is shown in FIG.
10
.
The iterated transformation and coding apparatus will be described first with reference to FIG.
9
.
An original image
300
supplied to this iterated transformation and coding apparatus of
FIG. 9
is input to a block generation circuit
200
where it is divided into a plurality of blocks
301
. These blocks are set so as not to overlap each other. Also, reduced images
307
obtained by reducing the original image
300
by a reduced-image generation circuit
202
are stored in a reduced-image storing circuit
204
. For the divided blocks
301
, in an approximation area search circuit
201
, reduced images are searched in a full search within the reduced-image storing circuit
204
and the most closely resembling reduced image is detected from among the reduced images. Approximation block position information
306
, obtained hereby, indicating which portion of the reduced image should be extracted, is transmitted to the reduced image storing circuit
204
, and a reduced image
305
of a specified area is taken out. Then, the reduced image
305
of the specified area is subjected to, for example, rotation/reverse/level-value conversion in accordance with a transformation parameter
304
in a rotation/reverse/level-value conversion section
203
, and a reduced image
303
after being transformed is output. As a result, the transformation parameter
304
and the approximation block position information
306
are output as an iterated function system (IFS) code
302
.
Next, a description will be given of the iterated transformation and decoding apparatus with reference to FIG.
10
.
The IFS code
302
output from the iterated transformation and coding apparatus of
FIG. 9
is once input to an IFS code storing circuit
205
and stored therein. The IFS code
302
is read therefrom sequentially in block units for a plurality of times. An IFS code reading circuit
206
reads an IFS code
308
in block units and separates it into the approximation block position information
306
and the transformation parameter
304
. Then, the approximation block position information
306
is input to a reduced-image storing circuit
210
, and the reduced image
305
of the specified area is taken out from the reduced image in accordance with the position information
306
. This reduced image
305
of the specified area is subjected to a transformation process based on the transformation parameter
304
by the rotation/reverse/level-value conversion section
203
, is added and copied onto the decoded image within a decoded-image storing circuit
208
and is stored. When the IFS code reading circuit
206
completes the reading of the IFS code
308
of all the blocks, the IFS code reading circuit
206
sends a reading completion notification signal
310
to a copying control circuit
207
. This copying control circuit
207
measures the number of times a series of the above copying process has been performed. When the number does not reach a preset value, a re-reading instruction signal
309
is output to the IFS code reading circuit
206
, and the copying process is performed again on all the blocks of the image. At the same time, re-processing instruction information is sent in accordance with a decoded-image output control signal
311
, and a decoded image
313
is connected, by a switch
209
, to an input
314
with respect to the reduced-image generation circuit
202
. The reduced-image generation circuit
202
generates a reduced image
315
in exactly the same manner as on the coder side, and the contents of the image stored in the reduced-image storing circuit
204
are replaced with this image. When, on the other hand, the copying process has reached a fixed number of times, the copying control circuit
207
issues a termination instruction in accordance with a decoded-image output control signal
311
, the decoded image
313
is connected to a final output image
316
by a switch
209
, and an output of the decoder is obtained.
In an example of conventional technology such as that described above, the approximation with respect to an image obtained by performing a reduction and transformation process on a block at an arbitrary place of the self entire image screen is measured. The position information of the most closely resembling block and the transformation parameter at that time are selected from all possible candidates. As a result, in the coder, a coded code is written into the bit stream in the sequence of the coded block.
Meanwhile, in the decoder, the coded bit stream is unscrambled, and a decoded image having the same size or the same aspect ratio as that of the input image on the coder side is output. However, in a texture mapping process (pasting of texture) for a three-dimensional shape, often used recently in CG (computer graphics), etc., three-dimensional shapes can take various forms and therefore, it is necessary to match the image with the shape.
In such a case, conventionally, the common practice is that by performing a filtering process, etc. on an image which is decoded once again, its aspect ratio is changed. If this changing of the aspect ratio can be performed at the same time as the decoding, the texture mapping process, etc., in CG can be simplified greatly.
SUMMARY OF THE INVENTION
An object of the present invention, which has been achieved in view of such circumstances, is to provide an iterated image transformation and decoding apparatus and method, in which changing of the aspect ratio can be performed at the same time as decoding without using a filtering process or the like during decoding, and a recording medium.
To achieve the above-mentioned object, according to one aspect of the present invention, there is provided an iterated image transformation and decoding apparatus comprising: two
Fukuhara Takahiro
Ohba Akio
Bayat Ali
Frommer William S.
Frommer & Lawrence & Haug LLP
Kessler Gordon
Mehta Bhavesh
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