Adjusting an electronic camera to acquire a watermarked image
First Claim
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.
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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.
62 Citations
19 Claims
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1. The method of adjusting the control setting of an electronic camera to acquire a watermarked image which comprises:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 15, 16)
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10. An electronic camera which has at least one control which can be adjusted to more accurately acquire a watermarked image:
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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.
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11. An electronic camera which has at least one control which can be adjusted to more accurately acquire a watermarked image:
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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. - View Dependent Claims (12, 13, 14)
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17. The method of adjusting the control setting of an electronic camera to more accurately acquire a watermarked image which comprises:
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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. - View Dependent Claims (18, 19)
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Specification