is the same
y red frames, the
, = 4. However,
nd the houses in
h influences the
nproved method
nage into blocks
re we divide the
ie value range of
ing image is as
Figure 5. The resulting image when Dy, is different
Through computation, the definition of the lower right block
is the maximum, so the cut-off frequency should be set to be
minimum. In this way the region around the ground objects
will not be blurred. The definition of the lower left block is
the minimum, so the cut-off frequency should be set
maximum. Through this we can reach a more satisfactory
dodging effect.
In order to reflect the experiment result more accurately, we
use some objective indicators to assess the original and
resulting images. At present, a common assessment method
is to first select five regions from the image, the upper left,
the lower left, the upper right, the lower right and the center,
then compare their mean and variance. However, there may
be differences between different regions in an image itself.
For example, if the upper left area of an image is forest and
the lower left area is houses, there should be different
lightness and contrast in an image. The approximately same
mean and variance of the two regions doesn't indicate a good
dodging effect.
Therefore, this paper adopts a new assessment method: select
several same ground objects from the different image regions
manually as shown in Figure 6, and calculate their mean and
variance(Table 1). If these values are approximately the same,
that means a satisfactory dodging effect was achieved.
Figure 6. The original image and the image after dodging
Mean standard deviation
Before After Before After
dodging | dodging | dodging | dodging
Vegetation] | 171.39 106.93 28.37 24.35
Vegetation? | 61.22 95.30 15.64 20.13
Vegetation3 | 33.45 88.35 6.8 19.08
Buildingsl 151.58 105.37 46.42 40.58
Buildings2 180.69 103.23 46.90 39.41
Buildings3 160.45 104.19 49.69 41.29
Table 1. The image information before and after dodging
It can be seen that the means of the same kind of ground
objects are approximately the same after dodging, in addition,
the uneven contrast of the whole image is greatly improved.
5. CONCLUSION
This paper puts forward an improved image dodging