Counting method of heterotrophic bacteria based on image processing

Heterotrophic bacteria is detected and counted by National Standard Method of China at present, i.e. flat dish numberation, which has the disadvantages of subjectivity, big error and low efficiency because of relying on manual counting. A method of rapid determination of heterotrophic bacteria in industrial cooling water is developed. After converting the original image into a greyscale one, we removed the edge image of culture dish on the basis of the principle that three unco-linear points can determine a circle. Then binarization with the greyscale-weighted threshold method, distance transform and watershed algorithm to segment overlapping colonies are applied, and finally four-connected searching algorithm was used to mark and count the colony. It has been proved that the method greatly improves the accuracy and efficiency of the heterotrophic bacteria counting and the counting results are not affected by shapes or sizes of the colony. It has been revealed that colony counting based on image processing method can be an effective way.