Method and apparatus for hiding one image or pattern within another

• US 5,905,819 A
• Filed: 02/05/1996
• Issued: 05/18/1999
• Est. Priority Date: 02/05/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Eastman Kodak Company
• Inventors: Daly, Scott J.
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Mariam, Daniel G.
• Application Number:
  US08/596,818
• Time in Patent Office: 1,198 Days
• Field of Search: 382/284, 382/270, 382/260, 382/232, 358/426, 358/456, 358/501, 358/532
• US Class Current: 382/284
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• 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 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• 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 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• 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 hiding a first image in a second image to produce a combined image includes the steps of: a) modifying the first image according to the content of the second image, so that when the modified first image is added to the second image to produce the combined image, no visible differences will exist between the second image and the combined image; and b) adding the modified first image to the second image to produce the combined image.

Claims

1. A method of modifying a first image according to a second image so that the first image will not be visible when added to the second image, comprising the steps of:

a) providing a human visual system model having a bank of spatial filters representing the responses of the human visual system to a plurality of frequencies;

b) applying the spatial filters to the first and second images to produce first and second sets of spatial filtered images;

c) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

e) accumulating the contrast attenuated spatial filtered images to produce the modified first image.

2. The method claimed in claim 1 employed in a method of hiding a first image in a second image, wherein the first image is an image representing a message, the second image is a pictorial image, and the modified first image is added to the second image to create a combined image that appears visually equivalent to the second image.

3. The method claimed in claim 1 employed in a lossy image compression method, wherein the first image is a potential error image resulting from the compression method, the second image is an image to be compressed, and the modified first image represents the maximum allowable error as a function of frequency and location in the compressed second image.

4. A method of hiding a first image in a second image to produce a combined image, comprising the steps of:

a) modifying the first image according to the content of the second image, so that when the modified first image is added to the second image to produce the combined image, no visible differences will exist between the second image and the combined image, wherein the step of modifying the first image comprises the steps of;

I) modifying the first and second images according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the first and second images according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) adding the modified first image to the second image to produce the combined image, wherein the step of adding the modified first image to the second image further comprises the steps of;

I) modifying the second image by the display model tone scale response and MTF and cone nonlinearity function;

ii) summing the modified first image with the modified second image to produce a combined image; and

iii) further modifying the combined image by the inverse of the cone nonlinearity.

5. The method claimed in claim 4, wherein:

a) the step of modifying the first image comprises the steps of;

i) modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the step of adding the modified first image to the second image further comprises the steps of;

i) modifying the second image by the display model tone scale response and MTF and cone nonlinearity function;

ii) summing the modified first image with the second image to produce a combined image; and

iii) further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

6. The method claimed in claim 4, wherein:

a) the step of modifying the first image comprises the steps of;

i) modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the step of adding the modified first image to the second image further comprises the steps of;

i) modifying the second image by the display tone scale response and the cone nonlinearity to produce a modified second image;

ii) summing the modified first image with the modified second image to produce a combined image;

iii) further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

7. The method claimed in claim 4, wherein:

the step of modifying the first image comprises the steps of;

a) modifying the second image with a low pass filter representing a contrast sensitivity function of the human visual system;

b) modifying the first image and further modifying the second image according to a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

c) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images;

e) accumulating the contrast attenuated spatial filtered images to produce the modified first image; and

f) further modifying the modified image by the inverse of the low pass filter representing a contrast sensitivity function of the human visual system.

22. The method claimed in claim 4, wherein the step of attenuating the contrast of the first image further comprises the steps of:

a) computing absolute values of the images in the first set of spatial filtered images to produce a set of absolute value images;

b) low pass filtering the set of absolute value images to produced a set of filtered images;

c) multiplying each image in the set of absolute value images by the corresponding masking image to produce product images; and

d) dividing each of the product images by the corresponding filtered image.

8. Apparatus for modifying a first image according to a second image so that the first image will not be visible when added to the second image, comprising:

a) a bank of spatial filters representing the responses of the human visual system to a plurality of frequencies;

b) means for applying the spatial filters to the first and second images to produce first and second sets of spatial filtered images;

c) means responsive to the second set of spatial filtered images for determining a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) means responsive to the set of masking images for attenuating the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

e) means for accumulating the contrast attenuated spatial filtered images to produce the modified first image.

9. The apparatus claimed in claim 8, employed in apparatus for hiding a first image in a second image, wherein the first image is an image representing a message, the second image is a pictorial image, and further comprising means for adding the modified first image to the second image to create a combined image that appears visually equivalent to the second image.

10. The apparatus claimed in claim 8 employed in a lossy image compression apparatus, wherein the first image is a potential error image resulting from the lossy image compression, the second image is an image to be compressed, and the modified first image represents the maximum allowable error as a function of frequency and location in the compressed second image.

11. Apparatus for hiding a first image in a second image to produce a combined image, comprising:

a) means for modifying the first image according to the content of the second image, so that when the modified first image is added to the second image to produce the combined image, no visible differences will exist between the second image and the combined image, wherein the means for modifying the first image comprises;

I) means for modifying the first and second images according to a display model having a tone scale response clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) means for further modifying the first and second images according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) means responsive to the second set of spatial filtered images for determining a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) means responsive to the set of masking images for attenuating the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) means for accumulating the contrast attenuated spatial filtered images to produce the modified first images;

vi) means for further modifying the modified image by the inverse of the contrast sensitivity function; and

b) means for adding the modified first image to the second image to produce the combined image, wherein the means for adding the modified first image to the second image further comprises;

I) means for modifying the second image by the display model tone scale response and MTF and cone nonlinearity function;

ii) means for summing the modified first image with the modified second image to produce a combined image; and

iii) means for further modifying the combined image by the inverse of the cone nonlinearity.

12. The apparatus claimed in claim 11, wherein:

a) the means for modifying the first image comprises;

i) means for modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) means for further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) means responsive to the second set of spatial filtered images for determining a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) means responsive to the set of masking images for attenuating the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images;

v) means for accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) means for further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the means for adding the modified first image to the second image further comprises;

i) means for modifying the second image by the display model tone scale responding MTF and cone nonlinearity function;

ii) means for summing the modified first image with the second image to produce a combined image; and

iii) means for further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

13. The apparatus claimed in claim 11, wherein:

a) the means for modifying the first image comprises;

i) means for modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) means for further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) means responsive to the second set of spatial filtered images for determining a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) means responsive to the set of masking images for attenuating the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) means for accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) means for further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the means for adding the modified first image to the second image further comprises the steps of;

i) means for modifying the second image by the display tone scale response and the cone nonlinearity to produce a modified second image;

ii) means for summing the modified first image with the modified second image to produce a combined image; and

iii) means for further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

14. The apparatus claimed in claim 11, wherein:

the means for modifying the first image comprises;

a) means for modifying the second image with a low pass filter representing a contrast sensitivity function of the human visual system;

b) means for modifying the first image and further modifying the second image according to a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

c) means responsive to the second set of spatial filtered images for determining a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) means responsive to the set of masking images for attenuating the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images;

e) means for accumulating the contrast attenuated spatial filtered images to produce the modified first image; and

f) means for further modifying the modified image by the inverse of the low pass filter representing a contrast sensitivity function of the human visual system.

15. A computer program product for modifying a first image according to a second image so that the first image will not be visible when added to the second image, comprising a computer readable storage medium having a computer program stored thereon for performing the steps of:

a) providing a human visual system model having a bank of spatial filters representing the responses of the human visual system to a plurality of frequencies;

b) applying the spatial filters to the first and second images to produce first and second sets of spatial filtered images;

c) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

e) accumulating the contrast attenuated spatial filtered images to produce the modified first image.

16. The computer program product claimed in claim 15 employed in a method of hiding a first image in a second image, wherein the first image is an image representing a message, the second image is a pictorial image, and the modified first image is added to the second image to create a combined image that appears visually equivalent to the second image.

17. The computer program product claimed in claim 15 employed in a lossy image compression method, wherein the first image is a potential error image resulting from the compression method, the second image is an image to be compressed, and the modified first image represents the maximum allowable error as a function of frequency and location in the compressed second image.

18. A computer program product for hiding a first image in a second image to produce a combined image, comprising a computer readable storage medium having a computer program stored thereon for performing the steps of:

a) modifying the first image according to the content of the second image, so that when the modified first image is added to the second image to produce the combined image, no visible differences will exist between the second image and the combined image, wherein the step of modifying the first image comprises the steps of;

I) modifying the first and second images according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the first and second images according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) adding the modified first image to the second image to produce the combined image, wherein the step of adding the modified first image to the second image further comprises the steps of;

I) modifying the second image by the display model tone scale response and MTF and cone nonlinearity function;

ii) summing the modified first image with the modified second image to produce a combined image; and

iii) further modifying the combined image by the inverse of the cone nonlinearity.

19. The computer program product claimed in claim 18, wherein:

a)the step of modifying the first image comprises the steps of;

i) modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the step of adding the modified first image to the second image further comprises the steps of;

i) modifying the second image by the display model tone scale response and MTF and cone nonlinearity function;

ii) summing the modified first image with the second image to produce a combined image; and

iii) further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

20. The computer program product claimed in claim 18, wherein:

a) the step of modifying the first image comprises the steps of;

i) modifying the second image according to a display model having a tone scale response, clipping, MTF, and quantization components representing a display medium for displaying the combined image;

ii) further modifying the second image according to a human visual system model having a cone nonlinearity function, a contrast sensitivity function, and a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

iii) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

iv) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images; and

v) accumulating the contrast attenuated spatial filtered images to produce the modified first image;

vi) further modifying the modified image by the inverse of the contrast sensitivity function; and

b) the step of adding the modified first image to the second image further comprises the steps of;

i) modifying the second image by the display tone scale response and the cone nonlinearity to produce a modified second image;

ii) summing the modified first image with the modified second image to produce a combined image;

iii) further modifying the combined image by the inverse of the cone nonlinearity and the inverse of the display tone scale response.

21. The computer program product claimed in claim 18, wherein:

the step of modifying the first image comprises the steps of;

a) modifying the second image with a low pass filter representing a contrast sensitivity function of the human visual system;

b) modifying the first image and further modifying the second image according to a set of spatial frequency filters representing spatial dependencies of a visual system to produce a first and second set of filtered images;

c) employing the second set of spatial filtered images to determine a set of masking images representing the maximum possible distortions that can be added to the second image without being visible;

d) employing the set of masking images to attenuate the contrast of the corresponding images in the first set of spatial filtered images to produce a set of contrast attenuated spatial filtered images;

e) accumulating the contrast attenuated spatial filtered images to produce the modified first image; and

f) further modifying the modified image by the inverse of the low pass filter representing a contrast sensitivity function of the human visual system.