Method of processing image information and method of preventing forgery of certificates or the like

• US 6,438,251 B1
• Filed: 12/02/1998
• Issued: 08/20/2002
• Est. Priority Date: 12/03/1997
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yamaguchi, Takashi
• Primary Examiner(s): Patel, Jayanti K.
• Application Number:
  US09/203,562
• Time in Patent Office: 1,357 Days
• Field of Search: 382/100, 382/162-167, 382/232, 382/243-250, 382/305, 382/306, 382/135, 380/54, 380/51, 380/252, 345/421, 358/444, 358/298, 713/200, 235/454, 235/469
• US Class Current: 382/100
• CPC Class Codes: B41J 2/2114 Ejecting specialized liquids, e.g. transparent or processing liquids B41J2/211 takes precedence
• CPC Class Codes: G06T 1/0021 Image watermarking
• 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: 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 1/32304 Embedding different sets of additional information
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/3261 of multimedia information, e.g. a sound signal
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3271 Printing or stamping
• CPC Class Codes: H04N 2201/3274 Storage or retrieval of prestored additional information
• CPC Class Codes: H04N 2201/3278 Transmission

Abstract

Additional information, composed of characters, images, voice, etc., is converted into two-dimensional codes and then converted into a visible additional image to be embedded. The additional image is embedded in a full-color main image in a state of invisibility to produce a composite image. The composite image is recorded on a non-electronic medium such as paper or on an electronic medium, such as a memory on a personal computer, over the Internet. The embedded additional image is extracted from the composite image recorded on the recording medium and the additional information is reproduced.

Claims

1. An image processing method comprising:

converting predetermined additional information into a visible additional image to be embedded in a main image;

creating a composite image by modulating the additional image by using a predetermined mask pattern information and embedding the additional image in the main image in a state of invisibility;

recording the composite image on a recording medium; and

extracting the embedded additional image from the composite image recorded on the recording medium to recover the predetermined information.

2. The method of claim 1, wherein converting includes converting the additional information into visible two-valued two-dimensional codes.

3. The method of claim 1, wherein converting includes converting the additional information into visible two-valued two-dimensional codes and extracting includes the additional image from the composite image using the mask pattern information.

4. The method of claim 3, wherein recording includes recording the created composite image in hard copy form on a non-electronic medium, and extracting reproduces the embedded additional information by physically superimposing a mask pattern corresponding to the mask information on the composite image recorded on the non-electronic medium.

5. The method of claim 4, wherein creating includes recording a portion of the mask pattern on a portion of the composite image in a state of visibility, and the extracting includes superimposing the corresponding portion of the mask pattern on the recorded portion of the mask pattern on the composite image, the recorded portion of the mask pattern being used as an alignment mark and to confirm the mask pattern.

6. The method of claim 4, wherein the mask pattern has a transmission factor distribution of the same pattern as the mask information and is a sheet-like mask that is placed on a separate non-electronic medium and has the same resolution and the same size as the mask information.

7. The method of claim 3, wherein recording includes recording the created composite image in soft copy form on an electronic medium, and extracting includes reproducing the embedded additional information by superimposing the mask information on the composite image recorded on the electronic medium.

8. The method of claim 7, wherein recording includes, in recording the composite image on a non-electronic medium, performing an error dispersion process on the composite image prior to recording.

9. The method of claim 1, wherein converting includes converting the additional information into visible two-valued two-dimensional codes, smoothing the two-dimensional codes, and modulating the two-dimensional codes with a predetermined mask pattern information.

10. The method of claim 1, wherein converting includes converting the additional information into visible two-valued two-dimensional codes, modulating the two-dimensional codes using predetermined mask pattern information, converting the value of each pixel of the modulated additional information into a positive or negative color difference amount for each R, G, and B components to form three color difference modulated images for R, G, and B components.

11. The method of claim 10, wherein the color difference amount for the R component is opposite in sign to those for the G and B components in the same pixel position on the color difference modulated images.

12. The method of claim 11, wherein creating creates the composite image by superimposing the three color difference modulated images for the R, G, and B components of a full-color main image.

13. The method of claim 12, wherein, for pixels in a region where the additional image exhibits a maximum or minimum level of brightness, their color difference amounts are set smaller than those of other pixels, thereby preventing overflow or underflow of the composite image.

14. The method of claim 1, wherein, in creating, the additional information is embedded in that position with the main image which is highly related in content to the additional image.

15. The method according to claim 1, wherein, in the creation step, the additional image is embedded in the main image together with information concerning the type, the size, the date of creation, and the embedding position of the additional information, and other attribute information.

16. The method of claim 1, further comprising converting a full-color main image into an achromatic image composed of R, G, and B components, and wherein the creating creates the composite image in such a way that it looks like a black and white image to the human visual system and its respective pixel is composed of multiple color components.

17. An image processing method comprising:

converting predetermined additional information into a visible additional image to be embedded in a main image;

creating a composite image by modulating the additional image by using predetermined mask pattern information and embedding the additional image in the main image in a state of invisibility, the composite image is produced in such a way that it looks a black and white image to the human visual system and its respective pixel is composed of multiple color components; and

recording the composite image on a recording medium.

18. The method of claim 17, wherein converting includes a converting the additional information into visible two-valued two-dimensional codes.

19. The method of claim 17, wherein converting includes converting the additional information into visible two-valued two-dimensional codes, smoothing the two-dimensional codes, and modulating the two-dimensional codes with predetermined mask pattern information.

20. The method of claim 17, wherein converting includes converting the additional information into visible two-valued two-dimensional codes, modulating the two-dimensional codes using mask pattern information, converting the value of each pixel of the modulated additional information into a positive or negative color difference amount for each of R, G, and B components to form three color difference modulated images for R, G, and B components.

21. The method of claim 20, wherein the color difference amount for the R component is opposite in sign to those for the G and B components in the same pixel position on the color difference modulated images.

22. The method of claim 21, wherein the creating creates the composite image by superimposing the three color difference modulated images for the R, G, and B components on a full-color main image.