Article
Ensemble image registration by a spatially
constrained clustering approach
Hao Zhu
1,2
, Qiqun Shi
2
, Yongfu Li
2
, and Qiuxuan Wu
1
Abstract
In this article, a novel spatially constrained clustering approach is proposed for ensemble image registration. We use a
spatially constrained Gaussian mixture model, which is based on a joint Gaussian mixture model and Markov random field,
to model the joint intensity scatter plot of the unregistered images. The spatially constrained Gaussian mixture model has
the capability of performing the correlation among neighboring observations. A cost function of reducing the dispersion in
the joint intensity scatter plot is proposed using the spatially constrained Gaussian mixture model to simultaneously
register a group of images. We derive an expectation maximization algorithm for the proposed model. Computer
simulations demonstrate the effectiveness of the proposed method.
Keywords
Spatially constrained Gaussian mixture model, Markov random field, ensemble registration, expectation maximization
Date received: 26 February 2016; accepted: 19 July 2016
Introduction
Image registration is a fundamental operation in image
analysis. It has been widely used in many applied
fields,
1–5
including remote sensing, computer vision, med-
ical image processing, and robotics.
Many algorithms have been proposed to deal with the
problem of image registration in the last decades.
6–11
They
can be roughly categorized as feature-based, Fourier-based,
and intensity-based methods. Traditional ways for register-
ing are choosing one image as a template, and every other
image is registered to it. This kind of way is widely used.
However, the disadvantage is obvious which image should
be chosen as the template. It has the problem of selection
dependency and internal inconsistency.
12
So, many algo-
rithms were proposed to perform the group image registra-
tion. Minimizing the sum of squared differences was applied
to register group images.
13
A sum of entropies criterion was
proposed to group images registration.
14
A sum of Jensen–
Shannon divergence is considered as cost function in the
study of Qian et al.
15
A joint intensity space, where each
axis corresponds to intensity from each of the images, was
proposed for ensemble image registration.
12
It is assumed
that each object in an image corresponds to a coherent col-
lection. The density of joint intensity space of group images
is modelled by a Gaussian mixture model (GMM). The like-
lihood of GMM maximized to reduce dispersion of the joint
intensity scatter plot (JISP).
12
An ensemble clustering
method with a regularization term based on mean elastic
energy of B-spline was proposed to register nonrigid multi-
sensor ensemble images.
16
Considering without choosing a
proper number of clusters in advance, infinite GMM was
proposed to simultaneously register a group of images.
17
However, the aforementioned methods were not considering
the relationship between neighboring pixels in an image.
To address this issue, we propose a clustering method
for the registration of ensemble images. The JISP of the
unregistered images is modelled using a spatially con-
strained Gaussian mixture model (SCGMM).
18
The
1
Department of Automation, Hangzhou Dianzi University, Hangzhou, China
2
Department of Automation, Cho ngqing Univ ersity of Posts a nd
Telecommunications, Chongqing, China
Corresponding author:
Hao Zhu, Department of Automation, Hangzhou Dianzi University, No.2,
Xiasha Street, Hangzhou, 310018, China; Department of Automation,
Chongqing University of Posts and Telecommunications, Chongqing,
400065, P. R. China.
Email: sandwish@163.com
International Journal of Advanced
Robotic Systems
2016: 1–7
ª The Author(s) 2016
DOI: 10.1177/1729881416663367
arx.sagepub.com
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