高動態範圍下的影像融合與色調重現

Abstract

色調重現目的是去調整或映射高動態範圍影像，調整影像圖素的亮度以及更好的對比度。本論文提出一個完善的彩色影像系統對於在極高動態範圍下場景的影像拍攝。用五張不同曝光的原始影像作融合來拓展動態範圍的概念，搭配色調重現和局部對比增強演算法以重現原始影像的對比和細節。 系統首先融合多張不同曝光的原始影像以獲得更多的動態範圍資訊，融合後原始影像的有效動態範圍可以擴展到256倍，接著對影像在不同亮度下重複抽取邊緣以擷取影像的細節，我們所提出的色調重現演算法將所擷取到的最佳邊緣統計圖作等化以分配到更均勻分佈的區域。最後區域對比增強使影像的細部更明顯。經由實驗結果，我們提出的高動態範圍影像系統能夠在色調重現及色彩鮮明度上得到好的結果。

Tone reproduction attempts to scale or map high dynamic range image data such that the resulting image has preserved the visual brightness and better contrast impression of the original scenes. In this paper, we propose an integrated color imaging system for taking images in extremely high dynamic range scenes. The system first fuses several differently exposed raw images to acquire more intensity information. The effective dynamic range of the image raw data can be extended to 256 times if five differently exposed images are fused. Then it runs edge detection iterations to extract the image details in different luminance levels. The proposed tone reproduction algorithm equalizes the histogram of the extracted fine edges which tends to assign larger dynamic range for highly populated regions. Finally, the local contrast enhancement is performed to further refine the image details. The experimental results show that the proposed high dynamic range imaging system has good performance on both tone and color reproduction.