Scan the 8×8 bitmap of Figure 4.159 using a Hilbert curve and calculate the runs of identical pixels and compare them to the runs produced by RLE. A space-filling curve completely fills up part of space by passing through every point in that part. It does that by changing direction repeatedly. We will only discuss curves that fill up part of the two-dimensional plane, but the concept of a space-filling curve exists for any number of dimensions.