Fig. 2.

Patch-based descriptor ${\overrightarrow{\Phi }}_{\Omega }$. Given a bounding box Ω, it is equally decomposed into n_φ patches ${\left\{{\phi }_i\right\}}_{i=1}^{n_{\phi }}$. For the i-th patch φ_i, low-level feature vector ϕ_i is extracted, and is assigned with a weight w_i. Then, the descriptor ${\overrightarrow{\Phi }}_{\Omega }$ is constructed by concatenating features of all patches, weighted by patch weights. Note that example patch weights are shown by the highlighted bounding box. Warmer colour indicates higher weight value.