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c)
The calculation speed must be considered as a large number of data points are
used in the edge detection.
In this paper, five edge detection algorithms were chosen, including Roberts operator,
Sobel operator, Prewitt operator, Log operator and Canny operator. Filtered images
were processed with the above five methods and the results were compared as shown
in Figure 6.
a
) Roberts operator
b
) Prewitt operator
c
)Sobel operator
d
) Log operator
e
) Canny operator
Fig. 6.
The edge detected images
From figure 6, we can find that the image processed with the Roberts operator is
better in terms of continuity and has the clearest outline. Roberts operator finds the
edge based on local difference method, and its advantages include high positioning
accuracy and high calculation speed, and thus the Roberts operator is chosen as the
image edge detection algorithm.
3)
The Estimation of Motion Parameters
The location extraction of remainders is to find the location range in a grayscale
image. Grayscale digital image can be transformed from RGB three-dimensional
space to a two-dimensional gray-scale matrix. The location range can be found in the
two-dimensional matrix with a set threshold.
A typical grayscale two-dimensional matrix of remainders image is shown in Table
1.The highlighted numbers in the table produces the contour of the remainder.
Generally speaking, grayscale values of the remainder and noise points are larger than
that of backgrounds. We have done a number of comparative experiments and found
that the remainders regional intensity ranges from 101 to 143, while majority of the
other values are less than 100.Therefore, the threshold is set to 100.When the
grayscale value is less than 100, the system will set the value to 0; while greater than
100, set to 255.This procedure generates a new grayscale image.
Table 1.
Typical remainders grayscale value matrix
23 13 24 34 54 65 23 23
22 2 32
109 106
67 45 41
12 46
110 120 108 104
34 45
66 21
109 105 107 121
45 34
16 24 33
116 111
26 16 111
34 11 34 56 23 67 32 43
After the contour of the remainders is found, the geometric center of remainders
can be calculated with extremes algorithm, and then the radius
r
of the remainder and
the vertical axis of centroid
y
can be calculated.
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