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Results
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Although the two measured data sets presented here are quite different, several human experts
agree that the results are reasonable. mrFindBorders is therefore able to deal with different
data sets and is not specialized for only one exemplary data set. In addition to the two exem-
plary flat data sets that are presented in this chapter, many more data sets have been tested.
7.4 Time of Computation
For the results presented in 7.3.1 (the registration method was “Grad. (Angular Dir.)”), the
whole matching procedure, i.e., 2 iterations on very-low-resolution images, 3 iterations on
low-resolution images, and 2 iterations on high-resolution images, took about 22 minutes. The
two iterations on the very-low-resolution images took only about 22 seconds, the three itera-
tions on the low-resolution images about 2 minutes and 15 seconds. The given times include
initial calculations, e.g., of bilinear weight matrices, which are performed at the beginning of
the matching procedure for each resolution. Therefore, after about 2 minutes and 37 seconds,
the program yielded decent results (see Figure 53 bottom left image). However, much more
time is needed to achieve the result shown in the bottom right image of Figure 53.
The reason why the time of computation is so much longer for the high-resolution case is
not only that the image size is larger (see below). As can be seen in the options menu, the dis-
tances between control points were always eight pixels. Therefore, the number of control
points for the very-low-resolution images (33 pixels x 33 pixels) is 25. The number of control
points for the low-resolution registration (65 pixels x 65 pixels) is 81, and for high-resolution
registration (129 pixels x 129 pixels) 289. For constant resolution, the time of computation
(excluding initial calculations) increases almost linearly with the total number of control
points that are considered because the time needed for each control point is almost constant
for a given resolution. Not all control points are always considered, i.e., the algorithm does not
try to find displacement values for all control points. For example, control points at the edges
are sometimes not used.
To give the reader an idea of how long the computation takes for different resolutions, 10 it-
erations were performed on all three resolutions. The number of control points was set to 81
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