Multiple watermarking techniques for documents and other data

• US 6,332,031 B1
• Filed: 07/14/2000
• Issued: 12/18/2001
• Est. Priority Date: 01/20/1998
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey, Gustafson, Ammon
• Primary Examiner(s): Patel, Jayanti K.
• Application Number:
  US09/616,462
• Time in Patent Office: 522 Days
• Field of Search: 382/100, 382/232, 382/162, 382/112, 382/218, 382/219, 355/40, 375/150, 702/191, 705/1, 713/176
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0071 using multiple or alternating watermarks
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00005 relating to image data
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00092 relating to the original or to the reproducing medium, e.g. imperfections or dirt detecting properties of a sheet H04N1/00681
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32304 Embedding different sets of additional information
• CPC Class Codes: H04N 1/32309 in colour image data

Abstract

Multiple digital watermarks, each of which has different characteristics, are embedded in a document. The characteristics of the various watermarks are chosen so that each of the watermarks will be affected in a different manner if the document is subsequently copied and reproduced.

The detection process or mechanism reads each of the watermark and compares their characteristics. While wear and handling may change the characteristics of the digital watermarks in a document, the relationship between the characteristic of multiple digital watermarks in a document will never-the-less give an indication as to whether a document is an original or a copy of an original.

Claims

1. A method of creating a watermarked image which comprises the steps of:

modifying an HSI (hue, saturation, Intensity) representation of an image to imbed a first watermark in said image and create a first watermarked image,

transforming said first watermarked image to the RGB (red, green, blue) color space, biasing the values which represent a second watermark toward a particular color,

modifying said HSI values to imbed said biased second watermark in said image and create a second watermarked image,

transforming said second watermarked image to the RGB color space, and

combining the values of said first and second watermarked images to create a final watermarked image.

2. The method recited in claim 1 wherein said biasing is toward a particular color.

3. A method of differentiating copies of an original document from the original document, said document containing a first digital watermark which has a first set of characteristics and a second digital watermark which has a second set of characteristics, said method comprising the steps of:

reading said first and second watermarks from said original document and comparing the resultant values to generate a first set of results,

reading said first and second watermarks from said copy of said original document and comparing the resulting values to generate a second set of results, and

using differences between said first and second sets of results to differentiate an original document from a copy of said original document.

4. The method recited in claim 3 wherein said first digital watermark has a first energy level and said second watermark has a second energy level.

5. The method recited in claim 3 wherein said first watermark has a first bit pattern and said second watermark has a different bit pattern.

6. The method recited in claim 3 where both said original document and said copy have been subjected to wear.