基於雙向濾波與限制對比度自適應直方圖等化的影像增強法

An Image Enhancement Method Based on Bilateral Filtering and Contrast Limited Adaptive Histogram Equalization

陳志凡(ZHI-FAN CHEN)

指導教授 ： 許巍嚴

國立中正大學/管理學院/資訊管理學系/碩士(2016年)

摘要

目前一般的的數位攝影科技並無法真實的呈現類似人眼所看到的場景，因為一般的顯示裝置都是低動態範圍(low dynamic range , LDR)，而非能忠實呈現較接近真實場景的高動態範圍(high dynamic range , HDR)，所以在一般的顯示器上，對於同時具有暗部及亮部資訊的高對比影像上，往往無法同時呈現暗部以及亮部的細節資訊。
如果用一般的影像增強方法來對這些影像做增強，可能會造成影像有亮度分布不均、是嚴重的顏色失真、流失影像的細部資訊的狀況發生。因此，本研究提出了一個針對高對比影像增強方法來解決此問題，利用雙向濾波器(bilateral filtering)來保留影像細節，再藉由能自動給予最佳運算參數的限制對比度自適應直方圖等化方法(contrast limited adaptive histogram equalization)，來對基礎層影像作適當的對比度調整，讓在一般顯示器上也能呈現出更近似於高動態範圍影像的視覺品質。
在實驗中，與其他相關方法做比較，本研究方法不論在細節資訊和色調的保留及亮度增強上，也都優於其他方法，在客觀的數學評估指標中也有較理想的數據表現。

關鍵字

影像增強 ； 高對比影像 ； 細節保留 ； 雙向濾波器 ； 限度對比度自適應直方圖等化

並列摘要

At present, digital photography technology can’t be precisely presented as the scene seen by the human eye since the display device is typically low dynamic range rather than high dynamic range. In other words, the devices are often unable to display the details of shadows and highlights at the same time for high contrast images.
If a normal image enhancement method is used to enhance these images, it may result in uneven distribution of image brightness, color distortion or loss of image detail information. Therefore, this study proposes a method to resolve these problems. Starting with the use of the bilateral filter to retain image details, then automatically give the optimum operation parameters through contrast limited adaptive histogram equalization to make appropriate contrast adjustment to the base layer image, so the display of the device can be more similar to the visual quality of the high dynamic range.
In the experiments, in comparison with other state-of-art methods, we find that the proposed method is superior to other methods whether in detail information, retention of hue or brightness enhancement. In addition, there is better performance in the objective mathematical evaluation indexes.

並列關鍵字

Image enhancement ； High contrast images ； Detail preservation ； Bilateral filtering ； Contrast limited adaptive histogram equalization

參考文獻

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