在攝影取像時，場景中通常會存在多重目標物，對相機而言，這些目標物位於不同的深度上，攝影者選擇一個深度作為對焦的依據，用景深來呈現的想要的情境。而一張相片所呈現的視覺品質，受限於相機鏡頭的種類與拍攝者的攝影技術。若拍攝時對焦不準確，便無法呈現出拍攝者的意念及感覺，導致它成為一張失敗的影像。為了解決這個問題，本文提出一個概念，讓攝影者在拍攝時不用考慮對焦的問題，只需隨意拍攝一張全對焦影像，再透過影像處理事後對焦至想要的目標或區域即可。
利用有限的影像資訊，我們提出一個以物件為基礎事後對焦架構，透過一個標籤賽局，來辨認出想要重新對焦的物件，透過空間濾波器使之在圖像中更為突出，並使背景模糊化模擬失焦的現象，進而達到景深設計的效果，提升整體圖像的視覺傳達品質。

Generally there are more than one object that locate at different depth in a scene of a photographic image. Photographers select a depth as the basis of focusing to present the desired scenarios. However, the visual quality of a photo is limited by the type of camera lens and the skills of the photographer. It cannot present the photographer’s feeling and lead to a failure if we cannot focus on the wanted object properly. To solve this problem, this thesis proposes a concept that photographers don’t need to consider the focusing problem when shooting but refocus on it after computer processing.
With limited image information, we propose an object-based refocusing framework to refocus on the wanted object. Through a image labeling game algorithm, we correctly identify the object which we want to refocus and make it more prominent in the image by using a spatial filter. Similarly, we simulate the out-of-focus effect by blurring the background. After these processes, we retrieve a correct focused image that can present the desired depth of field and improve the quality of visual communication.

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