Flags retrieval using color strings

The difference between a content-based, flag image system and a text-based flag image retrieval system is the capability that the previous one can rank flag images by the degree of similarity between the query flag image and flag images in the database, namely similarity-based retrieval. Conversely, a text-based flag image retrieval system is based on precise match. Our flags retrieval scheme is developed to retrieve flags efficiently. Firstly, vie transfer each flag to a color string using only 8 rules automatically. Secondly, we utilize the color strings for comparing the flags, namely color strings comparison (CSC). Our system offers both advantages of the content-based flags retrieval system (similarity-based retrieval) and a text-based flags retrieval one (very rapid and mature). The major differences between our proposed method and existing ones are shown as follows. 1) We consider the spatial information (our color strings comparison is permutation comparison). Most color quantization-based methods are combination comparison. 2) We resized the images to 20*20 pixels. Therefore, our approach can handle diverse sizes, defocus and noise problems. 3) We adopt the concept of the relative relation of RGB. Consequently, our system can deal with dissimilar lighting conditions, partial occlusion, and various color saturation at the same time. We succeed in transferring the flags retrieval problem to the strings comparison. 4) We create a bridge between a content-based retrieval system and a text-based retrieval one. Therefore, the content-based flags retrieval system becomes an analogous text-based retrieval system. Thus, the computational complexity is decreased significantly.