Low visible digital watermarks

• US 20060008112A1
• Filed: 06/14/2005
• Published: 01/12/2006
• Est. Priority Date: 04/19/2000
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M., Brundage, Trent J.
• Granted Patent: US 7,738,673 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/0042 Fragile watermarking, e.g. so as to detect tampering
• CPC Class Codes: G06T 1/0085 Time domain based watermarking, e.g. watermarks spread over several images
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• 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 1/32251 in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 1/32288 Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 1/32293 Repeating the additional information in a regular pattern
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes

Abstract

The present invention relates to digital watermarking. In a preferred embodiment, media is embedded with one or more digital watermark components. The media includes a blue color plane, a red color plane and a green color plane. The digital watermark component is embedded in the blue color plane, and scaled versions of the digital watermark component are embedded in the red and green color planes. The scaling of component in the red and green color planes helps insure that luminance attributable to the blue color digital watermark component is reduced or offset. A related watermark detection scheme is disclosed.

Claims

1. A method to embed a first digital watermark in media, wherein said media includes a blue color channel, a red color channel and a green color channel, said method comprising:

providing a signal change in terms of a color value, wherein the signal change corresponds to one or more watermark components to be applied to an area of the media;

first changing one or more color values in the area in the blue color channel according to the signal change; and

second changing one or more color values in the area in the red color channel and the green channel to reduce luminance attributable to the signal change in the blue channel.

2. The method of claim 1 wherein the changing one or more color values in the area in the red color channel and the green channel changes color values in each of the red and green channel by ⅛

of an amount of the signal change in the blue channel.

3. The method of claim 1 further comprising printing the media after said first changing and second changing, wherein a resulting printed media comprises the first digital watermark embedded therein.

4. The method of claim 3 wherein prior to said printing, the blue color channel, red color channel and green color channel are converted to at least yellow, magenta and cyan channels.

5. The method of claim 3 wherein said first digital watermark is detectable from analyzing at least chrominance characteristics associated with the printed media.

6. The method of claim 1, further comprising embedding a second digital watermark in the media, wherein said first digital watermark and said second digital watermark are separately detectable in a printed version of the media.

7. The method of claim 6 wherein the second digital watermark is detectable from analyzing luminance characteristics associated with the printed version of the media.

8. A method to detect a first digital watermark embedded in printed media, wherein the printed media comprises at least first color channel, a second color channel and a third color channel, said method comprising:

receiving optical scan data associated with the printed media, the received optical scan data being represented by a blue channel, a green channel and a red channel;

first scaling the blue channel with a first factor;

second scaling a sum of the red channel and the green channel with a second factor;

subtracting the scaled sum of the red channel and the green channel from the scaled blue channel and adding a shift factor to yield a detection signal; and

searching for a first digital watermark in the detection signal.

9. The method of claim 8 wherein said first scaling, second scaling, subtracting and adding are related according to:

first factor*blue channel−

second factor*(red channel+green channel)+shift.

10. The method of claim 9 wherein the first factor is in a range of 0.3-0.75, the second factor is in a range of 0.15-0.375, and the shift is in a color value range of 64-192.

11. The method of claim 10 wherein the first factor comprises 0.5, the second factor comprises 0.25 and the shift comprises 128.

12. The method of claim 8 wherein the detection signal represents chrominance characteristics.

13. The method of claim 12 further comprising searching for a second digital watermark from luminance characteristics of the blue channel, green channel and red channel.

14. A method to detect first steganographic indicia hidden in printed media, wherein the printed media comprises at least first color channel, a second color channel and a third color channel, said method comprising:

receiving optical scan data associated with the printed media, the received optical scan data being represented by a blue channel, a green channel and a red channel;

combining the blue channel, green channel and red channel to minimize image interference;

shifting the combined channels to reduce image saturation; and

searching for the steganographic indicia in the shifted, combined channels.

15. The method of claim 14 wherein the shifted, combined channels represents chrominance characteristics.

16. The method of claim 14 wherein the first steganographic indicia comprises a machine-readable code.

17. The method of claim 16 wherein the machine-readable code comprises digital watermarking.

18. The method of claim 14 wherein the steganographic indicia comprises an image or graphic.

19. A method to detect two or more different digital watermarks in media comprising:

receiving captured imagery of the media comprising a plurality of image frames;

for a first frame applying a first watermark detector to search for a first digital watermark hidden within the first frame; and

for a second frame applying a second, different watermark detector to search for a second, different watermark hidden within the second frame.

20. The method of claim 19 wherein the first frame and the second frame each represent a first portion of the media.