Six training images. Three positives and three negatives are given on the first and second row, respectively. In the images of first row, the association of red and brown regions is obvious. The image (c) has a few pericytes and many fibroblasts together. However, this image was selected as positive due to presence of targeted vessel. The image (d) has 903 red pixels that are spread out in the image. Therefore, there is not a perception of red region. Another negative image (f) 1888 red pixels in a few region, but they are not found with a brown stained regions.