Image Processing Reference
In-Depth Information
6.2.3.1 Temporal Image Signature Approach
The proposed approach, Temporal Image Signature (TIS) [
29
] explores the possi-
bilities of combining Image Signature approach (IS) [
19
] with the Temporal
Spectral Residual (TSR) [
11
] in order to determine the visual saliency. In this
section, a brief and comprehensive overview of the proposed TIS approach is
described.
It is proposed to extend the IS approach to the temporal domain. It is well-known
fact that as the size of the image increases, the FFT becomes progressively complex
at a much more rapid rate. DCT is more efficient in this case and the proposed
approach explores the advantage of DCT.
TIS approach can be divided into three main steps:
1. Frame division
2. Saliency detection
3. Transformation and accumulation
Frame Division Given a video clip as an input, at first, a number of frames
(XY) are sliced into the XT and YT planes. XT and YT are the planes of image
lines in a temporal domain. By doing this there is a better representation of the
horizontal-time (XT) and vertical-time (YT) axes which also contain movement
information.
Saliency Detection Provided the frames separately in horizontal-time and vertical-
time plane, the IS [
19
] approach is applied separately on all planes. This identifies
saliency in movements rather than in image creation. By extracting just salient
movement the camera movement is ignored.
Transformation and Accumulation Given the saliency information in their
respective planes, finally an accumulation is done after transforming back from
XT and YT domain to XY domain. This resulted in a final saliency map which
contains regions that grasp viewer
'
s attention. Figure
6.3
shows the proposed
system.
Saliency Map Computation Given a video clip with size
m
n
is the image size and
t
is the number of frames being processed, TIS [
29
] approach
can be written as follows.
n
t
where
m
MapXT
m
¼
sign
ð
DCT
ð
I
XTm
ÞÞ
ð
6
:
1
Þ
MapYT
n
¼
sign
ð
DCT
ð
I
YTn
ÞÞ
ð
:
Þ
6
2
ð
MapXT
m
Þ!
Transform
hMapXY
t
ð
6
:
3
Þ
ð
MapYT
n
Þ!
Transform
vMapXY
t
ð
6
:
4
Þ
Adding Eq. (
6.3
) and (
6.4
)
