Assessment of camera phone distortion for digital watermarking

• US 8,923,546 B2
• Filed: 07/05/2011
• Issued: 12/30/2014
• Est. Priority Date: 07/02/2010
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M.
• Primary Examiner(s): BHATNAGAR, ANAND P
• Application Number:
  US13/176,242
• Publication Number:
  US 20120076344A1
• Time in Patent Office: 1,274 Days
• Field of Search: 382/100, 382/232, 380/54, 380/210, 380/252, 380/287, 713/176, 704/200.1, 704/273, 381/73.1, 348/460, 348/463
• 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 2201/0051 Embedding of the watermark in the spatial domain
• 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

Abstract

The present disclosure relates generally to cell phones and cameras, and to digital watermarking involving such cell phones and cameras. One claim recites a method comprising: measuring distortion introduced by a cell phone camera; using a programmed electronic processor, quantifying the distortion; and providing quantified distortion as feedback to adjust a digital watermark embedding process in view of the distortion introduced by the cell phone camera. The act of quantifying distortion may include, e.g., quantifying a spatial frequency response (SFR) of the cell phone camera. Of course, other claims and combinations are provided too.

Claims

1. A method comprising:

measuring a spatial frequency response (SFR) of a cell phone camera;

calculating a measure associated with the SFR using one or more programmed electronic processors; and

using the one or more programmed electronic processors, altering a digital watermark embedding process based on the measure, in which the measure is calculated by computing an area under a SFR curve for the range of spatial frequencies associated with a digital watermark component and subtracting an area under the SFR curve due to aliasing.

2. The method of claim 1 in which the area under the SFR curve associated with the digital watermark component is computed using a trapezoidal rule over intervals of spatial frequencies.

3. A method comprising:

measuring a spatial frequency response (SFR) of a cell phone camera;

calculating a measure associated with the SFR using one or more processors; and

using the one or more processors, altering a digital watermark embedding process based on the measure, in which the measure is calculated as follows;

λ

=ρ

_synch−

ρ

_alias,

where ρ

_synch is an area under a SFR curve in the region of an associated digital watermark component, and ρ

_alias is an area under the SFR curve due to spatial frequencies aliasing with the digital watermark component.

4. The method of claim 3 in which the area under the SFR curve associated with the digital watermark component is computed using a trapezoidal rule over intervals of spatial frequencies.

5. An apparatus comprising:

memory; and

one or more electronic processors programmed for;

measuring a spatial frequency response (SFR) of a cell phone camera;

calculating a measure associated with the SFR by computing an area under a SFR curve for a range of spatial frequencies associated with a digital watermark component and subtracting an area under the SFR curve due to aliasing; and

altering a digital watermark embedding process based on the measure.

6. The apparatus of claim 5 in which the area under the SFR curve associated with the digital watermark component is computed using a trapezoidal rule over intervals of spatial frequencies.

7. An apparatus comprising:

memory; and

one or more electronic processors programmed for;

measuring a spatial frequency response (SFR) of a cell phone camera;

calculating a measure associated with the SFR as follows;

λ

=ρ

_synch−

ρ

_alias,

where ρ

_synch is an area under a SFR curve in a region of an associated digital watermark component, and ρ

_alias is an area under the SFR curve due to spatial frequencies aliasing with the digital watermark component; and

altering a digital watermark embedding process based on the measure.

8. The apparatus of claim 7 in which the area under the SFR curve associated with the digital watermark component is computed using a trapezoidal rule over small intervals of spatial frequencies.