TECHNICAL NOTE
DIGITAL & MULTIMEDIA SCIENCES
Hui Zeng,
1
Ph.D.; and Xiangui Kang,
1
Ph.D.
Fast Source Camera Identification Using
Content Adaptive Guided Image Filter*
ABSTRACT: Source camera identification (SCI) is an important topic in image forensics. One of the most effective fingerprints for linking
an image to its source camera is the sensor pattern noise, which is estimated as the difference between the content and its denoised version. It
is widely believed that the performance of the sensor-based SCI heavily relies on the denoising filter used. This study proposes a novel sensor-
based SCI method using content adaptive guided image filter (CAGIF). Thanks to the low complexity nature of the CAGIF, the proposed
method is much faster than the state-of-the-art methods, which is a big advantage considering the potential real-time application of SCI. Despite
the advantage of speed, experimental results also show that the proposed method can achieve comparable or better performance than the state-
of-the-art methods in terms of accuracy.
KEYWORDS: forensic science, image forensics, source camera identification, sensor pattern noise, denoising filter, content adaptive guided
image filter
The origin information of a digital image or video is important in
forensic research area as well as in applications; for example in law
enforcement, the investigator would be interested in linking images
of illegal content to a certain camera. One of the most effective fin-
gerprints for linking an image to its source camera is the sensor pat-
tern noise (SPN) (1), which is caused by photo-response
nonuniformity (PRNU) due to inhomogeneity of silicon wafers (2).
An important advantage of SPN is that it can identify not only cam-
era models, but also individual cameras of the same model (3).
In the most widely accepted sensor-based source camera iden-
tification (SCI) method (3), SPN is estimated as the difference
between the content and its wavelet denoised version (4), and its
correlation to the fingerprint of a given camera is used to mea-
sure the probability that an image originated from that camera.
Owing to its wide applications in source identification and integ-
rity verification, this method has been fully studied and various
enhancements have emerged recently. Existing enhancements to
SCI are classifiable in three categories:
1 Better filters are adopted in extracting SPN from the image
(5,6).
2 Better strategies or metrics are adopted to measure the corre-
lation between the SPN from an image and the fingerprint of
a reference camera (7–10).
3 Postprocessing the extracted SPN to further suppress the
unwanted artifacts, for example color interpolation, row and
column artifacts, and contamination of the image details
(7,11).
Our research lies in the first category enhancement of SCI.
Unlike other state-of-the-art SCI methods, in this method, SPN
is extracted from an image using a content adaptive guided
image filter (CAGIF) (12). Thanks to the low complexity nature
of CAGIF, the proposed method is much faster than other the
state-of-the-art methods, which is a big advantage considering
the potential real-time application of SCI. Despite the advantage
of speed, experimental results also show that the proposed
method achieves comparable or better performance than the
state-of-the-art SCI methods in terms of accuracy. In this study,
boldface symbols represent either vectors or matrices.
The rest of the paper is organized as follows. In the next section,
we briefly review of the process of sensor-based SCI and the
denoising filters used in the state-of-the-art literatures. The third
section introduces CAGIF and the proposed CAGIF-based SCI
method. The fourth section shows the experimental results. The
proposed method is compared with other methods in terms of both
accuracy and speed. The conclusion is given in last section.
Brief Review of Source Camera Identification
In this section, we briefly explain the SCI method developed in
ref. (3) and some improved algorithms that relate most to our work.
The PRNU of the imaging sensor is usually modeled as a
multiplicative factor that is unique to a camera A. Taking the
PRNU factor K
A
into consideration, the raw camera output I can
be written as:
I ¼ I
0
ð1 þ K
A
Þþh ð1Þ
where I
0
is the noise-free image, and h refers to other noise ele-
ments which usually believed to be zero-mean.
1
School of Information Science & Tech., Sun Yat-sen University, Guangz-
hou 510006, China.
*Supported by NSFC (Grant Nos 61379155 and U1135001), 973 Program
(Grant No. 2011CB302204), the Research Fund for the Doctoral Program of
Higher Education of China (Grant No. 20110171110042), and NSF of
Guangdong Province (Grant No. 2013020012788).
Received 28 Jan. 2015; and in revised form 9 June 2015; accepted 27
June 2015.
520 © 2015 American Academy of Forensic Sciences
JForensicSci, March 2016, Vol. 61, No. 2
doi: 10.1111/1556-4029.13017
Available online at: onlinelibrary.wiley.com