Method and apparatus for embedding data, including watermarks, in human perceptible images

• US 6,031,914 A
• Filed: 08/27/1997
• Issued: 02/29/2000
• Est. Priority Date: 08/30/1996
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Zhu, Bin, Tewfik, Ahmed H., Swanson, Mitchell D.
• Primary Examiner(s): Swann, Tod R.
• Assistant Examiner(s): Callahan, Paul E.
• Application Number:
  US08/918,122
• Time in Patent Office: 916 Days
• Field of Search: 380/4, 380/5, 380/6, 380/7, 380/9, 380/10, 380/14, 380/17, 380/20, 380/54, 380/59, 704/203, 707/104, 341/4, 341/8, 341/9, 341/56-67, 348/25-30, 348/334, 348/444, 348/460-467, 348/473-475, 348/586-592, 382/100-117, 382/140, 382/162-167, 382/173-180, 382/232, 382/283
• US Class Current: 380/54
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• 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 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• CPC Class Codes: H04N 1/32165 using cosine transforms
• CPC Class Codes: H04N 1/3217 using wavelet transforms
• CPC Class Codes: H04N 1/32187 with selective or adaptive application of the additional information, e.g. in selected frequency coefficients
• CPC Class Codes: H04N 1/32192 according to calculated or estimated visibility of the additional information in the image
• CPC Class Codes: H04N 19/122 Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 21/23892 involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• 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

Abstract

A technique for hiding of data, including watermarks, in human-perceptible images, that is, image host data, is disclosed. In one embodiment a method comprises three steps. In the first step, data to be embedded is inputted. In the case of a watermark, this data is a unique signature, and may be a pseudo-noise (PN) code. In the case of hidden data to be embedded in the host data, this data is the hidden data itself, or the hidden data as spread against the frequency spectrum by a pseudo-noise (PN) code. In the second step, the inputted data is embedded within the host data, in accordance with a perceptual mask of the host data. The perceptual mask determines the optimal locations within the host data to insert the inputted data. In the case of images, these optimal locations are determined by reference to the human visual system. In the third step, the host data, with the embedded data, is further masked by a non-frequency mask. In the case of image data, the non-frequency mask is a spatial mask.

Claims

1. A computerized method for embedding inputdata into host data representing a human-perceptible image comprising:

inputting the input data;

embedding the input data into the host data in accordance with a perceptual mask conducted in the frequency domain; and

,

further wherein the input data is embedded in the host data in accordance with a perceptual mask in a domain other than the frequency domain.

2. The computerized method of claim 1, wherein the input data embedded into the host data comprises data representing a watermark acting as a unique identifier for the host data.

3. The computerized method of claim 2, wherein the watermark comprises a pseudo-noise (PN) sequence.

4. The computerized method of claim 1, wherein the input data embedded into the host data comprises data spread against data representing a signature according to a spread-spectrum technique.

5. The computerized method of claim 4, wherein the signature comprises a pseudo-noise (PN) sequence.

6. The computerized method of claim 1, wherein the perceptual mask comprises a model in which a contrast threshold at a frequency f is expressed as a function of the frequency f, a masking frequency f_m and a masking contrast c_m,

7. The computerized method of claim 1, wherein the non-frequency mask comprises a spatial mask.

16. The method according to claim 1 wherein the data is processed according to the perceptual mask in the frequency domain prior to being processed according to the mask conducted in the non-frequency domain.

17. The method according to claim 1 further including producing frequency masking thresholds from processing of the host data.

18. The method according to claim 1 further including producing masking thresholds for the non-frequency domain from processing of the host data.

19. The method according to claim 17 wherein the data to be embedded is adjusted according to the frequency masking thresholds.

20. The method according to claim 18 wherein the data to be embedded is adjusted according to the non-frequency masking thresholds.

21. The method according to claim 20 wherein the data to be embedded is first adjusted using the frequency masking thresholds.

22. The method according to claim 1 wherein the perceptual mask in the non-frequency domain is processed prior to the perceptual mask in the frequency domain.

23. The method according to claim 18 further wherein the non-frequency domain is the spatial domain, and the masking thresholds are spatial thresholds.

8. A computerized system for hiding input data having a plurality of bits within a host data representing a human-perceptible image comprising:

a processor;

a computer-readable medium;

computer-executable instructions executed by the processor from the computer-readable medium comprising;

segmenting the host data into a plurality of blocks;

applying a discrete cosine transform (DCT) to each block of the host data to generate a frequency block corresponding to the block of host data;

applying a perceptual mask to each frequency block;

embedding each bit of the input data into a corresponding frequency block; and

,

applying and inverse DCT to each frequency block to generate the host data having the put data embedded therein.

9. The computerized system of claim 8, wherein the instructions further comprise spreading each bit of the input data by a signature after selecting a plurality of blocks of the host data.

10. The computerized system of claim 8, wherein the instructions further comprise applying a spatial mask to the host data having the input data embedded therein.

11. A computer-readable medium having a computer program stored thereon to cause a suitably equipped computer to perform the method comprising:

segmenting host data representing a human-perceptible image into a plurality of blocks;

spreading each of a plurality of bits of input data by a signature after selecting a plurality of blocks of the host data;

applying a discrete cosine transform (DCT) to each block of the host data to generate a frequency block corresponding to the block of host data;

applying a perceptual mask to each frequency block;

embedding each bit of the input data, as spread by the signature, into a corresponding frequency block;

applying an inverse DCT to each frequency block to generate the host data having the input data embedded therein; and

,

applying a spatial mask to the host data having the input data embedded therein.

12. The computer-readable medium of claim 11, wherein the medium is a floppy disk.

13. A computerized system for embedding a watermark into a host data representing a human-perceptible image comprising:

a processor;

a computer-readable medium;

computer-executable instructions executed by the processor for the computer-readable medium comprising;

segmenting the host data into a plurality of blocks;

applying a discrete cosine transform (DCT) to each block of the host data to generate a frequency block corresponding to the block of host data;

applying a perceptual mask to each frequency block;

applying the DCT to each bit of a plurality of bits of the watermark;

scaling each frequency block, as to which the perceptual mask has been applied, by a corresponding bit of the watermark, as to which the DCT has been applied, and by a spatially masked block corresponding to the frequency block, to generate an adder block corresponding to the frequency block;

adding each frequency block with the adder block corresponding to the frequency block;

applying an inverse DCT to each frequency block as has been added to with the adder block corresponding to the frequency block to generate a watermarked block of the host data corresponding to the frequency block; and

,

applying a spatial mask to each watermarked block to generate the spatially masked block corresponding to the frequency block to which the watermarked block corresponds;

embedding each bit of the input data into a corresponding frequency block; and

,

applying an inverse DCT to each frequency block to generate the host data having the input data embedded therein.

14. A computer-readable medium having a computer program stored thereon to cause a suitably equipped computer to perform the method comprising:

segmenting host data representing a human-perceptible image into a plurality of blocks;

applying a discrete cosine transform (DCT) to each block of the host data to generate a frequency block corresponding to the block of host data;

applying a preceptual mask to each frequency block;

applying the DCT to each bit of a plurality of bits of a watermark;

scaling the each frequency, as to which the perceptual mask has been applied, by a corresponding bit of the watermark, as to which the DCT has been applied, and by a spatially masked block corresponding to the frequency block, to generate an adder block corresponding to the frequency block;

adding each frequency bock with the adder block corresponding to the frequency block;

applying an inverse DCT to each frequency block as has been added to with the adder block corresponding to the frequency block to generate a watermarked block of the host data corresponding to the frequency block; and

,

applying a spatial mask to each watermarked block to generate the spatially masked block corresponding to the frequency block to which the watermarked block corresponds;

embedding each bit of the input data into a corresponding frequency block; and

applying an inverse DCT to each frequency block to generate the host data having the input data embedded therein.

15. The computer-readable medium of claim 14, wherein the computer-readable medium is a floppy disk.