以光流法設計平面運動攝影機之數位影像穩定技術

Abstract

在過去這幾年以來，數位影像的穩定在數位攝影機中扮演了一個重要的角色。在本研究中，提出一個更有效率的演算法，以便對因攝影機非自願性的平面晃動，而造成影像的不穩定，實現其影像的穩定化處理。在此所指的穩定定義如下，對於固定場景的晃動影像，希望能將所有晃動的影像序列，補償到和影像未晃動之前的影像越接近越好。對於非固定場景的晃動影像，希望能將所有不是影像移動方向的晃動部分補償回去，使得補償過後的影像看起來更平穩。而此法建立在光流法的基礎上，以消除在所擷取的影像中，所產生的不穩定現象。在提出的數位影像穩定技術當中，主要包含了運動量測單元、運動判斷單元及運動補償單元。運動量測單元可以判斷影像序列中，其晃動的運動向量。運動判斷單元則可以決定搖晃的影像是屬於哪一種晃動。最後經由運動補償單元，可以產生出一穩定的影像。總而言之，此研究的目標是對於因攝影機平面晃動所擷取到的影像做穩定化的處理。而這裡所提到的晃動影像皆只包含了一種晃動種類。實驗的結果顯示出此數位影像穩定技術有良好的穩定效果。

In the past years, the stabilization of digital image has become an important role of the digital camcorder. In this study, a more efficient algorithm is proposed to implement the im-age stabilization for the image instability caused by the involuntary planar movement of camcorder holders. The stabilization of an image is defined as follows. If the image with fixed scene was vibrated at some time, the object of digital image stabilizer (DIS) is to compensate all after vibrated image frames in order to make these image frames similar to the image frame at that time. As to the image with unfixed scene, the object of DIS is to compensate the vibrations which are not the same direction as the movement of camcorder in order to make the image looks smooth. This approach is based on optical flow method to eliminate the un-pleasing conditions of captured image. The proposed digital image stabilizer (DIS) mainly contains motion estimation unit, motion decision unit, and motion compensation unit. The motion estimation unit can determine the motion vectors among image sequences. The motion decision unit is designed to determine what kind of motion the shaken image belongs to. The stable image can be generated through the motion compensation unit. Consequently, the ob-ject of DIS is to stabilize the shaken image, which is captured by a planar motion camcorder and just contains one type motion. Experimental results show that the DIS has a good per-formance.