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HDevelop User's Manual

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106 CHAPTER 5. PROGRAM EXAMPLES<br />

Figure 5.12: Board with electonic devices (left) and the corresponding color value image in the<br />

HSV space (right).<br />

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If you look closer at this program segment you will notice some obvious enhancements that can<br />

be made. One is necessary due to the color model: The thresholding of the color image chooses<br />

all pixels with a certain color. This selection is independent of the color saturation. Thus it<br />

might happen that very bright pixels (nearly white pixels) or very dark pixels (nearly black<br />

pixels) have the same color value as the components. But you are only looking for stronger<br />

colors. For this you select all pixels first whose color is strong, i.e., all pixels with a high<br />

saturation.<br />

The second enhancement concerns the objects’ shape. As the devices are rectangular you<br />

can specify the smallest enclosing rectangle of all connected components to enhance the segments.On<br />

the left side of figure 5.13 the resulting components are marked.<br />

In a second step, we will search for all ICs. This seems to be easy, as they are rather large<br />

and dark. However, some problems emerge due to the bright labels that are printed across<br />

some ICs. Thus a simple thresholding alone is not sufficient. In addition you have to combine<br />

the segments belonging to one IC. This is done by examining the spatial adjacencies of the<br />

segments. A dilation is used to enlarge the regions until they overlap each other. This dilation<br />

must not be so large that different ICs are merged. Thus gaps caused by labels have to be<br />

smaller than gaps between ICs. Now you can separate the enlarged ICs in their connected<br />

<strong>HDevelop</strong> / 2000-11-16

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