where the upper left corner corresponds to index 0 and the indices increase from left to right, then top to
bottom. For example, notice that the first 1 encountered in the first row of the table is at index 5. This
corresponds to the pixel (x, y) shown earlier as an example of a local articulation point. The bits b0 and b2
are set to 1 since the corresponding pixels at (x − 1, y − 1) and (x + 1, y − 1) are 1, all other bits being zero.
The byte index 00000101 is the decimal number 5.