Figure 4. The steps in the image-processing used to extract the region of the primary branches defined by method 2.

(a) RGB image of spread out panicle. (b) Grey scale image. (c) Binary image. (d) The image after applying the morphological opening with a 1 × 1 disk. (e) Image with holes filled. (f) The image with small objects removed. (g) The extraction results represented as (b–b)*(-f). (h) The panicle skeleton and the vertices. Junctions (red + ), Terminals (green + ).