When measuring an area of contiguous pixels, regions connected only along a diagonal will not be included.

If the pixel marked with an X is clicked (see the Table 1) only the pixels connected by the left, right, bottom or right sides will be selected, as the Table 2 shows.

Table 1: Image pixels



















Table 2: Selected pixels



















The program determines which pixels lie within a "blob" by searching the four nearest neighbors to find a pixel satisfying the required intensity requirements. This pixel is then added to a list of selected pixels to be searched around during the next phase.