Method for embedding digital information in an image

• US 5,859,920 A
• Filed: 11/30/1995
• Issued: 01/12/1999
• Est. Priority Date: 11/30/1995
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Squilla, John R., Denber, Michel, Honsinger, Chris W., Hamilton, John, Daly, Scott J.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Mariam, Daniel G.
• Application Number:
  US08/565,804
• Time in Patent Office: 1,139 Days
• Field of Search: 382/203, 382/279, 382/284, 382/115, 358/455, 358/456, 358/457, 358/458, 380/3, 380/23
• US Class Current: 382/115
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0081 whereby both original and watermarked images are required at decoder, e.g. destination-based, non-blind, non-oblivious
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32208 involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32251 in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 2201/3205 of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3225 of data relating to an image, a page or a document
• CPC Class Codes: H04N 2201/3226 of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/328 Processing of the additional information

Abstract

A method of embedding digital data in a source image includes the steps of: a) generating a multi-level data image representing the digital data; b) convolving the multi-level data image with an encoding carrier image to produce a frequency dispersed data image; and c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data. The data is recovered from the image by: a) cross correlating the source image containing embedded data with a decoding carrier image to recover the data image; and b) extracting the digital data from the recovered data image.

Claims

1. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image;

wherein the variable frequency encoding carrier image is generated by the steps of;

b1) providing a 1-dimensional variable frequency carrier signal, wherein the 1-dimensional variable frequency carrier signal is a linear chip signal defined by;

##EQU3## where r is the distance in units of pixels, f_min is the minimum frequency of the chirp, f_max is the maximum frequency of the chirp, and L is the total length of the chirp in the units of pixels; and

b2) converting the 1-dimensional variable frequency carrier signal to a 2-dimensional variable frequency carrier signal using a rotational sweep; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data.

2. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image;

wherein the variable frequency encoding carrier image is generated by the steps of;

b1) providing a 1-dimensional variable frequency carrier signal, wherein the 1-dimensional variable frequency carrier signal is a logarithmic chirp signal defined by;

##EQU4## where r is the distance in units of pixels, f_min is the minimum frequency of the chirp, f_max is the maximum frequency of the chirp, and L is the total length of the chirp in the units of pixels;

b2) converting the 1-dimensional variable frequency carrier signal to a 2-dimensional variable frequency carrier signal using a rotational sweep; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data.

3. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image;

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data;

d) cross correlating the source image containing embedded data with a variable frequency decoding carrier image to recover the data image;

e) extracting the digital data from the recovered data image; and

f) locating a subset of the source image containing embedded data having the lowest high-frequency component variance and cross correlating the subset with the decoding carrier image.

4. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the step of adding is performed by optical techniques, and wherein the variable frequency dispersed data image is added to the source image in a photographic printer by placing a transparency having the frequency dispersed image in the film gate of the printer.

5. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the step of adding is performed by optical techniques, and wherein the frequency dispersed data image is added to the source image in a photographic printer by pre-exposing photographic paper used in the printer with the frequency dispersed image.

6. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the variable frequency encoding carrier image is generated by the steps of;

b1) providing a 1-dimensional variable frequency carrier signal; and

b2) converting the 1-dimensional variable frequency carrier signal to a 2-dimensional variable frequency carrier signal using a rotational sweep; and

c) applying a tapered weighting function to the variable frequency carrier signal.

7. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the adding step is performed optically, and wherein the step of adding the frequency dispersed data image to the source image utilizes a scaling factor dependent on film characteristics.

8. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the adding step is performed optically, and wherein the adding step is performed by contact exposing a transparency bearing the frequency dispersed data image onto photographic paper.

9. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the adding step is performed optically, and wherein the adding step is performed by simultaneously exposing the source image and the frequency dispersed data image onto photographic paper in photographic printer.

10. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data, wherein the adding step is performed optically, and wherein the adding step is performed by affixing a transparency bearing the frequency dispersed data image onto the source image.

11. A method of embedding digital data in a source image, comprising the steps of:

a) generating a multi-level data image representing the digital data;

b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image; and

c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data;

d) cross correlating the source image containing embedded data with a variable frequency decoding carrier image to recover the data image; and

e) extracting the digital image from the recovered data image;

wherein the recovered data image has rows and columns of values, further comprising the steps of;

e1) finding the difference between the minimum and maximum values for each row of the recovered data image to produce row difference values;

e2) finding the difference between the minimum and maximum values for each column of the recovered data image to produce column difference values;

e3) finding the n highest difference values for the rows and saving the indices of these rows, where n is determined from the size of the multi-level data message;

e4) finding the n highest difference values for the columns and saving the indices of these columns, where n is determined from the size of the multi-level data message; and

e5) locating data centers in the recovered data image by intersecting the saved rows and columns.