Digital Watermark Detection Using Predetermined Color Projections

• US 20070147653A1
• Filed: 06/28/2006
• Published: 06/28/2007
• Est. Priority Date: 01/26/2001
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Hannigan, Brett, Reed, Alastair
• Granted Patent: US 7,995,790 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 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection

Abstract

The present invention relates to digital watermarking. In one implementation, a system is provided to read a digital watermark from digital imagery which includes data representing a number of pixels. Each pixel of the number of pixels is defined by a set of values representing color components of the particular pixel. The digital watermark is embedded in the digital imagery through modifications to at least some data representing the digital imagery. The system includes a filter to calculate values of pixels along a preferred projection axis, the preferred projection axis corresponds to a direction of embedding determined based on color characteristics of at least some pixels associated with the digital imagery; and a digital watermark reader which operates on values calculated by the filter. Other implementations are provided as well.

Claims

1. A system to read a digital watermark from digital imagery which includes data representing a number of pixels, wherein each pixel of the number of pixels is defined by a set of values representing color components of the particular pixel, and wherein the digital watermark is embedded in the digital imagery through modifications to at least some data representing the digital imagery, said system comprising:

a filter to calculate values of pixels along a preferred projection axis, the preferred projection axis corresponds to a direction of embedding determined based on color characteristics of at least some pixels associated with the digital imagery; and

a digital watermark reader which operates on values calculated by the filter.

2. The system recited in claim 1 wherein said filter examines pixels in a neighborhood of pixels surrounding one or more of the pixels to determine the preferred projection axis.

3. The system recited in claim 2 wherein the digital watermark includes a spatial pattern of a predetermined size and wherein said filter examines pixels in an area of said spatial pattern to determine the preferred projection axis.

4. A method of reading a digital watermark from a color image that includes a plurality of pixels and which was digital watermarked using a scale to black digital watermarking technique, said method comprising:

filtering the color image to generate filtered data by projecting color values of a set of pixels onto a selected axis that is determined by examining color of surrounding pixels—

and not through filtering with a predetermined process without an examination of the color values, and

reading the watermark from resulting filtered data.

5. A method of reading a digital watermark from a digital image or video that includes a plurality of pixels, each pixel of the plurality of pixels is defined by a set of numbers representing color components, said method comprising:

filtering the set of numbers that represents each pixel by projecting the set of numbers to a selected axis, wherein a direction of said selected axis is determined by examining color values of pixels in an area associated with each pixel, and

wherein said filtering provides results; and

reading a digital watermark from the results provided by said filtering.

6. The method recited in claim 5 wherein said filtering determines the direction of said selected axis for each pixel by examining values of pixels in a neighborhood of pixels surrounding each pixel.

7. A digital watermark reading method to read a digital watermark that has embedded as one or more luminance values of at least some pixels of an image or video by projecting color changes representing the digital watermark onto a luminance axis of each of the some pixels, said method comprising:

filtering the image prior to reading the digital watermark by first projecting color values of each pixel onto a preferred projection axis that is determined by examining color values of predetermined pixels, wherein at least the values are used to determine a direction of the axis; and

reading the watermark from data associated with a result of said filtering.