Figure 3
From: A bag-of-words approach for Drosophila gene expression pattern annotation
Illustration of the bag-of-words approach. First, a visual codebook is constructed by applying a clustering algorithm to a subset of the local features from training images, and the center of each cluster is considered as a unique "visual words" in the codebook. Each local feature in a test image is then mapped to the closest visual word, and each test image is represented as a (normalized) histogram of visual words.