Automatic Extraction of Tongue Coatings from Digital Images: A Traditional Chinese Medicine Diagnostic Tool

In traditional Chinese medicine, the coating on the tongue is considered to be a reflection of various pathologic factors. However, the conventional method to examine the tongue lacks an acceptable standard and does not provide the means for sharing information. This paper describes a segmentation method to extract tongue coatings. First, the tongue body was extracted from the original image using the watershed transform. Then, a threshold method was applied to the image to eliminate the light from the camera flash. Finally, a threshold method using the Otsu model in combination with a splitting-merging method was used in the red, green, and blue (RGB) space to extract the thin coating. The combination of the above two methods is applied in the hue, saturation, and value (HSV) space to extract the thick coating. The feasibility of this method is tested by experiments, and the accuracy of segmentation is 95.9%.