Figure 1: Examples of hand gestures in a low-light scene.
It is obviously difficult to extract the necessary appearance
information of a hand gesture. The objective of this study is
to recognize hand gestures in low-light scenes.
Figure 2: Examples of the temporal integration of the low-
light hand gesture sequence shown in Figure 1. We can see
that sufficient information is captured while the motion blur
is generated. Further, we can see that both the direction and
the magnitude of the motion blur represent discriminative
characteristics to differentiate hand gestures. The key idea
of this study is to exploit this motion blur for hand gesture
recognition.
age (Tang et al., 2014). Moreover, there are previous
studies using KINECT (Ren et al., 2013) or Leap Mo-
tion (Marin et al., 2014).
In these previous studies, however, the researchers
have implicitly assumed a bright lighting condition to
precisely capture the hand gestures. In other words,
hand gesture images should be taken at a high S/N
ratio. In low-light scenes, as illustrated in Figure 1,
the S/N ratio of the captured images degrades because
heavy noise is likely to be imposed on low-light im-
ages. In such case, previous methods are ineffective
at recognizing hand gestures.
In order to address such problems caused by low-
light scenes, we propose a novel hand gesture recog-
nition method by using a single color image that is
constructed by integrating a hand gesture sequence
temporally. In general, the temporal integration of
images improves the S/N ratio; thus, it enables us to
acquire sufficient appearance and motion information
of a hand gesture even in low-light scenes.
However, the temporal integration of a hand ges-
ture produces motion blur. In general, motion blur
has been widely considered to be one of the annoying
noises that degrade performance in various computer
vision or image processing techniques. In contrast, in
this study, we make effective use of motion blur to
recognize hand gestures. Figure 2 shows examples of
the integrated gesture image containing motion blur.
We consider that both the direction and the magnitude
of motion blur represent discriminativecharacteristics
that can be used for differentiating hand gestures.
In order to extract both the direction and the mag-
nitude of the motion blur of a hand gesture, we ana-
lyze the gradient intensity distributions of the image
as well as color distributions. In fact, an analysis of
the gradient intensity distribution of a motion-blurred
image plays an important role in the estimation of the
moving directions of objects, as reported in (Lin et al.,
2011). Furthermore, the color distribution of the in-
tegrated gesture image is considered to be helpful in-
formation for measuring the magnitude of the motion
blur. As shown in Figure 2, motion-blurred regions
can be viewed as a mixture of the hand and back-
ground components. The magnitude of the motion
blur is likely to be large when the skin color intensity
(hand motion region) is low, and vice versa. This im-
plies that the analysis of color distributions allows us
to estimate the magnitude of the motion blur.
By using both the gradient intensity and the color
distributions, we compute a self-similarity map (Walk
et al., 2010), which encodes pairwise statistics of spa-
tially localized features by a similarity within a single
image. Because a self-similarity map can represent
spatial relationships via a similarity, it can assign in-
variant characteristics to the individual variations in
gesture motions, such as differences in lighting con-
ditions and gesture speeds. We exploit the computed
self-similarity maps as training data for constructing
a hand gesture recognition system.
On the other hand, a single motion-blurred image
can also be obtained by taking the image with a long-
exposure time. However, it is hard to ensure that the
entire hand gesture can be observed within such ex-
posure time. In other words, it is difficult for cam-
eras to find the times when the hand gesture starts
and ends. In contrast, the temporal integration al-
lows us to estimate both the start and the end timings
of a hand gesture by analyzing the captured images.
Thus, we utilize the temporal integration scheme in-
stead of using a single motion-blurred image taken
with a long-exposure time. Although the temporal in-
tegration makes motion blur discretized as shown in
Figure 2, it is enough to obtain both the direction and
the magnitude of the motion blur of a hand gesture.
The main contribution of this study is as follows.
We exploit a single color image obtained by tempo-
rally integrating the hand gesture sequence to recog-
nize hand gestures in low-light scenes. In particular,
we make effective use of the motion blur included
in the integrated gesture image. To the best of our
knowledge, this study is the first to use motion blur
in the context of hand gesture recognition. Unlike