由於低價掃瞄器的普及化，使得相關的影像處理技術已被廣泛地應用於各行各業文件資料數位化的領域中。惟文件數位化的過程中，經常遭遇到影像網底及摺痕移除的問題，基於此，本論文將針對文件影像中的前景物件及背景物件進行分析、研究，進而利用影像中不同物件間的特徵，有效分離出所欲保存的物件。
在本篇論文中，我們選擇地籍藍圖與工程藍圖作為實驗樣本，由於藍晒圖本身多為大尺寸文件，因此一般都會在保存文件的過程中留下深刻之摺痕，惟因摺痕與背景之間並無明顯色差，因此我們採用CIE Lab色彩空間的模式轉換來進行分析工作；此外，為了提高文件數位化後的再利用性，我們也在CIE Lab色彩模式下採用了植基於統計柱狀圖的門檻值法（Thresholding based on the Histogram）來濾除藍晒圖的背景網底及摺痕。
最後藉由實驗模擬來測試驗證，我們的作法可以有效的濾除背景網底並保留藍晒圖的主要資訊，而且在運算速度上也有不錯的表現。

Due to the prevalence of low price scanners, the image processing technology has been widely applied to the document digitalization in various fields. However, in the document digitalizing process the shading and crease problems are encountered frequently. The purpose of the study is to separate and extract the objects desired to keep from the scanned images by analyzing the different characteristic between the forward objects and the background objects of the images.
In this study, we choose the cadastres and drawing as the experimental samples. Blueprints are in large scale mostly, therefore it leaves them the considerably thick creases after quite a long time preservation. There are not obvious chromatism between crease and background, so we transform the image into CIE Lab color space to carry on the analysis. In addition, in order to enhance the reusability of the digitalized documents, we used thresholding based on the histogram under the CIE Lab color space to filter background shading and crease of the blueprint.
Experimental results show that our method may effectively filter the background shading and retain main information of blueprint, and has good performance in the operating speed.

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