半自動產生具夕陽特效之影像合成系統

Abstract

本篇論文提出一個半自動產生具有夕陽特效圖片的影像合成系統，此系統係延伸於Farid和Mahmood所提出的觀點，在將兩張圖片做影像合成時，一張為背景圖片，另一張為特效圖片。背景圖片作為合成影像中的基底圖片，特效圖片是具有特殊視覺效果的圖片，用於將此特效加在基底圖片中。其缺點是同時亦將不需要的背景物體也加在基底圖片中，使得結果看起來不自然。 本論文主要探討夕陽特效。為了在合成影像中僅保留原特效圖片的夕陽特效，首先，我們利用夕陽特效在原特效圖中各位置的顏色、飽和度跟亮度為基礎，產生一只具夕陽特效的新圖片。此張新特效圖片將具有原特效圖片中相似的特殊視覺效果，且原特效圖片中的背景物體已被去除。然後，對新特效圖片和背景圖片作餘弦轉換，轉換後的餘弦係數再經過高斯低通濾波器處理，來決定兩圖片欲保留部分，最後依照各自比例加在一起，且做亮度調整即得合成影像。 本系統亦提供一個使用者介面，可以迅速產生所要夕陽特效圖片，並且藉由調整參數，來完成使用者想要的合成影像。

In this thesis, we propose a semi-automatic system to generate sunlight effect image for image composition. The system refers to the idea proposed by Farid and Mahmood. In the two pictures do image composition, one is background picture, another is special effect picture. Background picture as a the base picture of composite image. The special effect picture is a picture with special visual effects. The special effects are added to the base picture. The disadvantage is the unwanted background objects are also added to the base picture. So the results do not look natural. In this thesis, we mainly discussed the sunset effects. In image composition, we retain only the sunlight effects in the sunset picture. First, we use each position's color, saturation and intensity of the original effect image as a basement to generate a new sunlight effects image. The new picture will have visual effects similar to the original effect picture, and the background objects of the original effect picture have been removed. Then, the new special effect pictures and background images do cosine transform. Cosine coefficients converted and then processed through a Gaussian filter to determine both want to retain part of the picture. Finally, added together according to their proportion and adjust intensity to get the composite image. The proposed system provides a user interface can quickly generate sunlight effect image for image composition by adjusting parameters.