Image analysis – Applications
Reexamination Certificate
1999-07-01
2002-07-02
Patel, Jayanti K. (Department: 2721)
Image analysis
Applications
C348S408100, C382S232000
Reexamination Certificate
active
06415042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital image coding apparatus using watermarking, a decoding apparatus, and coding and decoding methods, and more particularly, to a digital image encoding apparatus for inserting an original signature image into a significant area of a host image during encoding, evaluating variance between the host image and the original signature image during decoding, thereby precisely estimating the quality of the host image, a corresponding decoding apparatus, and corresponding encoding and decoding methods.
2. Description of the Related Art
Watermarking is a technology in which an image to be transmitted is transmitted together with an encrypted image for the purpose of providing security and authentication rights. A receiver side receives the image to be transmitted (hereinafter to be referred to as a host image) together with the encryption image transmitted with confidence (hereinafter to be referred to as a signature image). The signature image is decoded by a special decryption apparatus.
FIG. 1
is a conceptual block diagram illustrating a conventional digital image codec apparatus
1
for generating a watermarked image
8
and extracting a signature image
14
from the watermarked image. In the conventional digital image codec apparatus, during encoding, a DCT (Discrete Cosine Transform)
2
is performed on a host image
3
and a secret signature image
4
to be transmitted, thereby extracting DCT coefficients for the respective images. The DCT coefficients are encoded by an encoder
5
. Here, the DCT coefficient components of the signature image
4
are encoded by a separate encryption encoder
6
that controls the encryption operation. In such a manner, the DCT coefficients of the host image
3
and the DCT coefficients of the signature image
4
inserted into the DCT coefficients of the host image
3
after being encoded, can be transmitted. An IDCT (Inverse Discrete Cosine Transform)
7
is performed on the DCT coefficients
2
A of the host image and the DCT coefficients
2
B of the signature image inserted into the DCT coefficients of the host image, thereby obtaining a watermarked image
8
in which only the host image is visible, while the signature image is not visible.
The signature image
4
watermarked on the host image
3
is decoded by a special decryption apparatus to then be restored. During restoration, IDCT is performed on a watermarked image, thereby extracting DCT coefficients thereof. Next, the extracted DCT coefficients
2
A obtained by performing DCT on the original host image
3
, are separated from the DCT coefficients of the watermarked image at subtractor
10
, thereby extracting DCT coefficient components of the encoded signature image. Then, a decoder
11
decodes the DCT coefficient components of the encoded signature image. Here, the encryption decoder
11
performs a control operation for the decryption process. The DCT coefficients of the signature image decoded by the decryption control operation are again IDCT-performed
13
, thereby restoring the signature image.
As described above, in the conventional digital image codec apparatus using watermarking, a conventional method for evaluating the quality of a transmitted image is performed by comparing the transmitted current image with the previous image in various ways. The conventional method is based on the assumption that the current image is not significantly different from the previous image. However, this assumption is not applied to an abruptly changing image screen. In this case, image evaluation is not accurately performed. Also, even if the assumption is proper, the image evaluation is less correct than in the case of a comparison with the original image.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide a digital image coding apparatus which can precisely estimate the quality of a host image by transmitting a small quantity of image samples, which are suitable for the application of an analysis of variance (ANOVA) technique, as a signature image using watermarking during encoding without affecting an original image, and by performing an ANOVA technique on the restored signature image and the original signature image during decoding.
To achieve the above object of the present invention, there is provided a digital image coding apparatus for recording a signature image on a host image using watermarking, including a first discrete wavelet transform portion for receiving a host image to be transmitted and performing discrete wavelet transform thereon, thereby outputting M×M discrete wavelet coefficients where M is a predetermined positive integer, an original signature image storage portion for storing an image, which is suitable to the performance of an analysis-of-variance (ANOVA) technique as an original signature image, a second discrete wavelet transform portion for receiving the original signature image and performing discrete wavelet transform thereon to obtain N×N wavelet coefficients, N being another predetermined integer smaller than M, and a coefficient replacement/combination portion for replacing and combining N×N location data with N×N wavelet coefficients selected among M×M wavelet coefficients in accordance with a predetermined rule to then output the N×N location data and replaced M×M wavelet coefficients.
Also, the digital image coding apparatus may further include an inverse discrete wavelet transform portion for performing inverse discrete wavelet transform on the replaced M×M wavelet coefficients to generate a combined host image.
Also, the digital image coding apparatus may further include a compression portion for compressing the combined host image and the N×N location data.
The predetermined positive integer N is preferably smaller than or equal to ⅛ of the predetermined positive integer M.
Also, the predetermined rule preferably is to select 50% of the upper significant wavelet coefficients among M×M wavelet coefficients.
According to another aspect of the present invention, there is provided a digital image decoding apparatus for receiving bitstreams having a signature image recorded on a host image using watermarking and for restoring the host image and the signature image, including a coefficient separating portion for separating N×N wavelet coefficients from the M×M wavelet coefficients using the N×N location data, M being a predetermined positive integer and N being another predetermined integer smaller than M, an inverse discrete wavelet transform portion for performing inverse discrete wavelet transform on the N×N wavelet coefficients to generate a restored signature image, an original signature image storage portion for storing the signature image, which is suitable to the performance of an ANOVA technique and which is the same as that used in watermarking of the host image as the original signature image, and an ANOVA portion for applying the original signature image and the restored signature image to an ANOVA technique to output variance characteristic data of the restored signature image as image quality indication data.
Also, the digital image decoding apparatus may further include a decompression portion for receiving the bitstreams having the combined host image and the N×N location data compressed therein, and decompressing the same to output the combined host image, and N×N location data representing the locations of signature image discrete wavelet coefficients, and a discrete wavelet transform portion for performing discrete wavelet transform on the combined host image to obtain M×M wavelet coefficients, M being a predetermined positive integer.
According to another aspect of the present invention, there is provided a digital image codec apparatus for recording a signature image on a host image using watermarking, and restoring the host image and the signature image, including: a first discrete wavelet transform portio
Patel Jayanti K.
Samsung Electronics Co,. Ltd.
LandOfFree
Digital image coding/decoding apparatus and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital image coding/decoding apparatus and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital image coding/decoding apparatus and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2872455