Direction-based segmentation of retinal blood vessels

An unsupervised method is introduced for retinal blood vessels segmentation. The direction map is built by assigning to each pixel a discrete direction out of twelve possible ones. Under- and over-segmented images are obtained by applying two different threshold values to the direction map. Almost all foreground pixels in the under-segmented image can be taken as vessel pixels. Missing vessel pixels in the under-segmented image are recovered by using the over-segmented image. The method has been tested on the DRIVE dataset producing satisfactory results, and its performance has been compared to that of other unsupervised methods.