Matching of digital images to acquisition devices
View Patent ↗In a digital image matching method, reference calibration data associated with one or more reference digital image files is ascertained. The reference digital image files each have reference calibration data that is hidden metadata and can also have public metadata that is readable by a different procedure. A test digital image file is obtained and a data structure capable of holding the reference calibration data is detected in the test digital image file. The presence of second calibration data within the data structure of the test digital image file is determined. If the reference and second calibration data match, then the test digital image file and reference digital image files are from the same digital acquisition device.
1. A method executable by a computer for identifying a digital acquisition device that captures an image using red, green, and blue channels, the method comprising the steps of:
obtaining at least a makernote tag data containing a first non-public whitepoint calibration data of a suspected digital acquisition device with the computer;
locating a makernote tag data in an image file to be matched with the computer;
searching for a second non-public whitepoint calibration data within the makernote tag data located in the image file to be matched with the computer;
comparing the first non-public whitepoint calibration data with the second non-public whitepoint calibration data with the computer; and
identifying the suspected digital acquisition device as a source of the test image file if the first and second non-public whitepoint calibration data match with the computer,
wherein each of the first and second non-public whitepoint calibration data contains a calibration value of the green channel, a calibration value of the red channel, and a calibration value of the blue channel,
wherein the searching step includes:
detecting a pattern of the green channel calibration value, the red channel calibration value, and the blue channel calibration value contained in the image file to be matched; and
first detecting the calibration value of the most transmissive channel among the green, red, and blue channels, and then expanding around a location of the detected most transmissive channel to detect the calibration values of other channels among the green, read, and blue channels.
2. A computer-readable storage medium storing a computer program executable by a computer for identifying a digital acquisition device that captures an image using red, green, and blue channels, the computer program containing:
an obtaining code for obtaining at least a makernote tag data containing a first non-public whitepoint calibration data of a suspected digital acquisition device;
a locating code for locating a makernote tag data in an image file to be matched;
a searching code for searching for a second non-public whitepoint calibration data within the makernote tag data located in the image file to be matched;
a comparing code for comparing the first non-public whitepoint calibration data with the second non-public whitepoint calibration data; and
an identifying code for identifying the suspected digital acquisition device as a source of the test image file if the first and second non-public whitepoint calibration data match,
wherein each of the first and second non-public whitepoint calibration data contains a calibration value of the green channel, a calibration value of the red channel, and a calibration value of the blue channel,
wherein the searching code is further configured to:
detect a pattern of the green channel calibration value, the red channel calibration value, and the blue channel calibration value contained in the image file to be matched; and
first detect the calibration value of the most transmissive channel among the green, red, and blue channels, and then expand around a location of the detected most transmissive channel to detect the calibration values of other channels among the green, read, and blue channels.