利用區域資訊進行內涵式影像檢索的檢索歷程學習機制之研究

「區域方法」與「相關回饋」是「內涵式影像檢索」的重要議題。區域表示法不僅能包含影像內局部資訊, 更能表示區域之間的空間相鄰關係, 是以相較於一般以整張影像為基礎的方法, 區域方法提供了更佳的影像比對準則與檢索功能性。由於使用者提供的範例影像常無法完整表達搜尋的意圖, 相關回饋技術旨在藉由與使用者的互動, 令其標記目前檢索結果中各影像的重要性, 以更新檢索結果。目前相關回饋的方法主要可分為兩類, 第一種方法是檢索過程所學得的參數不會使用在其他檢索過程; 第二種方法則是利用過往檢索所學得的參數, 以利更快得到好的檢索結果。本研究主要探討如何在相關回饋中使用區域表示法技術。在單一檢索歷程中, 我們提出的方法主要根植於Bayesian 架構, 並包含了會隨時間變化的使用者模型。使用者模型主要包含「檢索目標」與「使用者意涵」兩種概念。「檢索目標」意指藉由分析回饋影像的共同特徵, 來描述使用者心目中的搜尋目的; 而「使用者意涵」則代表一組在相關回饋中學得的參數, 主要用於更新比對影像的度量。影像的比對是在區域表示法的架構下進行,藉由考慮影像區域之間的空間相鄰關係,以求得較好的影像間區域對應結果。此外, 我們亦使用了一種能將回饋影像區域分群的方法,此方法可使在數學上, 將「檢索目標」與「使用者意涵」的學習, 完全以區域表示法架構進行。我們亦討論如何利用過往檢索歷程所學得的參數進行更佳的學習。本研究所提出的檢索, 能在區域表示法架構下, 藉由過往檢索結果推得一「隱含語意空間」。我們主要的想法是, 一個區域就代表了一個隱含的語意概念, 故一次檢索事實上是包含了數個語意概念。我們藉由過往短期檢索的結果初始化隱含語意空間,並以此空間進行長期檢索,且不斷將新學得的語意概念加入此空間中。由於長期下來, 此空間容易包含不一致、重覆或擾亂的資訊, 故我們使用一種維度削減的技術, 在區域表示法架構下, 將「隱含語意空間」化簡至比較緊密的表示法。實驗結果顯示出, 透過使用者模型與區域表示法, 短期檢索能達到相當好的檢索效能。而長期檢索則能更進一步藉由「隱含語意空間」改進檢索結果。實驗也顯示出, 我們提出的維度削減技術, 的確能消除冗餘的隱含語意概念。

關鍵字

區域方法；相關回饋；檢索歷程；檢索目標；使用者意涵；隱含語意空間；內涵式影像檢索

並列摘要

Region-based approaches and relevance feedback have been indispensable issues in content-based image retrieval (CBIR). Region-based representation combines both local information and their spatial organization so as to provide better image representation and matching criterion. Relevance feedback allows users to rate retrieved images and refine the retrieved results interactively. Current relevance feedback methods are mainly divided into intrasession and intersession learning, depending on whether or not the learned information from historical query sessions is accumulated to subsequent query sessions. This study addresses region-based issues for both intrasession and intersession learning. The proposed intrasession learning technique is a generalized Bayesian framework which incorporates a time-varying user model. The user model includes a target query to specify the user’s ideal query and a user conception to adjust the time-varying matching criterion. We include spatially adjacent relationship to estimate the region correspondence between images for better image matching criterion. In addition, we also propose to update the target query as well as the user conception in region level based on the estimated region correspondence. For intersession learning, we aim to infer the hidden semantic space in region level by accumulating the knowledge learned from previous query sessions. The main idea is that a region in the query possesses a hidden semantic concept, and hence a query session will generate several concepts in our work. We initialize the hidden semantic space based on a series of query sessions. With the constructed hidden semantic space, we then perform retrieval and keep accumulating newly learned concepts into the hidden semantic space. Since the hidden semantic space may contain inconsistency, overlapping or mislabeled concepts, we employ a dimension reduction technique in region level to construct a more compact space. Experiments demonstrate that the proposed intrasession learning method combined with time-varying user model and region-based representation achieves satisfactory results. The results also show that our intersession learning method based on the inferred hidden semantic space further improves the retrieval accuracy, and the proposed dimension reduction technique removes redundant hidden semantic concepts effectively.

並列關鍵字

region-based approaches ； relevance ； query session ； target query ； user conception ； hidden semantic space ； content-based image retrieval

參考文獻

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via EMD flow,” in Proc. IEEE Workshop on Content-Based Access of Image and

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experiments,” IEEE Transactions on Image Processing, vol. 9, no. 1, pp.

國際替代計量

利用區域資訊進行內涵式影像檢索的檢索歷程學習機制之研究

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