Counting colonies of bacteria or other microorganisms growing on an agar plate are used to estimate the density of microorganisms within a liquid culture. It is important that the counting is accurate, consistent, and fast. However, the colony counting is usually done manually and is laborious and subject to user bias and misuse, which results in inaccurate counts. To mitigate the tedium associated with manual counting and reduce the user bias, we proposed to develop an automatic colony counting method for bacteria or other microorganisms growing on an agar plate by image processing.