Adjusting an electronic camera to acquire a watermarked image

• US 6,366,680 B1
• Filed: 11/22/1999
• Issued: 04/02/2002
• Est. Priority Date: 11/22/1999
• Status: Expired due to Term

• Current Assignee: Engelhard Corporation (BASF SE), Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Hannigan, Brett T., Brunk, Hugh, Rogers, Eliot
• Primary Examiner(s): Bella, Matthew C.
• Application Number:
  US09/444,770
• Time in Patent Office: 862 Days
• Field of Search: 382/100, 348/229, 348/345, 348/356, 348/349
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 2200/24 involving graphical user interfaces [GUIs]
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/90 Dynamic range modification of images or parts thereof

Abstract

The present invention provides a mechanism for automatically setting the exposure time and gain of an electronic camera so that the acquired image has improved characteristics for the detection of a digital watermark. With the present invention the exposure time and gain of an electronic camera are set by first directing the camera at a test target with the camera'"'"'s controls set to a default set of values. The system then calculates a histogram of the luminance values of the pixels in the image. Next characteristic values from the histogram such as the peak value, the centroid value, the RMS value, the median value, etc. are calculated. One or more of the characteristic values of the histogram are then applied as an index or pointer to values of pre-established settings that are stored in a table. Values from the table are used to set the exposure time and/or gain of the camera. In some embodiments, the variance of the luminance histogram is also measured and used to index data from the table.

Claims

1. The method of adjusting the control setting of an electronic camera to acquire a watermarked image which comprises:

adjusting said control setting to a default value,

acquiring a first watermarked image with said camera,

the luminance values of the individual pixels in said first watermarked image forming a histogram of individual pixel luminance values,

calculating a magnitude value for at least one parameter of said histogram,

using said value to obtain a second value for said control setting,

adjusting said camera in accordance with said second value,

acquiring a second watermarked image with said control setting set to said second value.

2. The method claimed in claim 1 including the step of reading a digital watermark from said additional image.

3. The method claimed in claim 1 wherein said parameter is the centroid of said histogram.

4. The method claimed in claim 3 including the step of reading a digital watermark from said additional image.

5. The method in claim 1 wherein said parameter is the peak value of the centroid of said histogram.

6. The method in claim 1 wherein said control setting is the exposure time of said camera.

7. The method in claim 1 wherein the first image acquired by said camera is an image of a photographer'"'"'s gray card.

8. The method in claim 1 wherein said parameter is the variance of said histogram.

9. The method in claim 1 wherein control setting includes the gain of said camera.

15. The method recited in claim 1 wherein said first image is an image of a photographer'"'"'s gray card.

16. The method recited in claim 1 wherein said default setting is an exposure time of {fraction (1/90)} second.

10. An electronic camera which has at least one control which can be adjusted to more accurately acquire a watermarked image:

means for adjusting said control setting to a default value,

means for acquiring a first watermarked image with the camera,

the luminance values of the individual pixels in said first watermarked image forming a histogram of individual pixel values,

means for calculating the value of at least one parameter of said histogram,

means for using said value to obtain a second value for said control setting,

means for adjusting said camera in accordance with said second value,

means for acquiring a second watermarked image with said control setting set to said second value.

11. An electronic camera which has at least one control which can be adjusted to more accurately acquire a watermarked image:

a computer which controls said camera,

a program for controlling said computer to facilitate,

adjusting said control to a default value,

acquiring a first watermarked image with the camera with said control adjusted to said default value,

the luminance values of the individual pixels in said first image forming a histogram of individual pixel luminance values,

calculating the value of at least one parameter of said histogram,

using said value to obtain a second value for said control setting,

adjusting the control of said camera in accordance with said second value,

acquiring at least one additional watermarked image with said control setting set to said second value,

detecting a watermark in said additional watermarked image.

12. The camera recited in claim 11 wherein said parameter is the centroid of said histogram.

13. The camera recited in claim 11 wherein said parameter is the peak value in said histogram.

14. The camera recited in claim 11 wherein said control is the exposure time of said camera.

17. The method of adjusting the control setting of an electronic camera to more accurately acquire a watermarked image which comprises:

acquiring a first watermarked image with the camera,

the luminance values of the individual pixels in said first image forming a histogram of individual pixel values,

calculating the value of at least one parameter of said histogram,

using said value to obtain a new value for said control setting,

adjusting said camera in accordance with said new value,

attempting to read a watermark from said first watermarked image, and

if said read operation is not successful, acquiring a second watermarked image with said control setting sent to said new value, and reading a watermark from said second watermarked image.

18. The method recited in claim 17 wherein said parameter is the centroid of said histogram.

19. The method recited in claim 17 wherein said control setting is the exposure time of said camera.