Implementation Efficiency of Binary Morphology

The efficiency of implementations of binary morphology is investigated, using both full image rasterops and word accumulation methods. All processing speeds are expressed in a way that is relatively independent of CPU speed and the sizes of both image and structuring element; namely, elementary pixel operations per CPU cycle (EPO/cyc). Options for handling boundary pixels are discussed. It is shown that use of successive full image rasterops is much slower than methods where the full struc-turing element is applied repeatedly to small parts of the image. Processing speeds of the former range from about 1 to 3 EPO/cyc, whereas the latter are typically between 4 and 7 times faster and range from 3 to 12 EPO/cyc. For small images using rasterops, vertical operations are about twice as fast as horizontal (3.2 vs 1.6 EPO/cyc); using word accumulation, vertical operations are only slightly faster than horizontal (12 vs 10 EPO/cyc). Performance on large images is reduced by a factor of between 2 and 4, due to slow reads and writes to main memory