Abstract: Automatic classification can be done by extracting Thangka headdress features,the main steps:1) select the headdress region through human-computer interaction and obtain initial segmentation image by preprocessing the segmentation result which is segmented through iterative segmentation or segmentation algorithm based on RGB；2) separate the crown by the Euler number which is extracted from the initial segmentation image；3) extract Fourier descriptors from out contour of the initial segmentation image,separate hairpin or monk hat through the distance between the feature and each cluster center．The realization of headdress automatic classification can improve the classification efficiency and meet the needs of automatic semantic annotation and semantic retrieval．According to the demand of application,we designed a retrieval system,which can realize retrieval based on text,content and semantics,and improve the accuracy of retrieval.

Key words: Thangka retrieval,Headdress classification,Semantic annotation,Hierarchical retrieval system