結合直方圖均化與影像融合之影像強化方法

Image Enhancement Based on Histogram Equalization and Image Fusion

林志明(Chih-Ming Lin)

指導教授 ： 謝政勳

朝陽科技大學/資訊學院/資訊工程系/碩士(2010年)

摘要

本論文提出一個結合直方圖均化與影像融合之影像強化方法 (Image Enhancement Based on Histogram Equalization and Image Fusion)稱為IE/HEIF。在IE/HEIF方法中，分為三個步驟：第一、將原始影像反轉取得反轉影像；第二、將原始影像與反轉影像透過線性內插進行融合並執行限制範圍性直方圖均化；第三、利用線性內插再次融合原始影像與第二步驟所獲得的均化影像。為了增進IE/HEIF方法強化的效果，我們以區塊影像標準差為基礎，提出一個適應性調整線性融合參數的方法，這個方法稱為IE/HEIF_std。期能進一步強化影像對比與改善影像品質。
為了驗證本論文所提的方法，我們以數個影像範例進行模擬，並且與以直方圖為基礎之影像強化方法進行比較。模擬結果顯示我們所提出的IE/HEIF與IE/HEIF_std方法均能有效改善影像品質。一般而言，IE/HEIF_std方法如所期待的具有較佳的影像強化效果。此外，本論文所提方法與以直方圖均化為基礎之方法比較，有較佳的視覺品質。在模擬的範例中，我們所提出的IE/HEIF與IE/HEIF_std方法能夠避免影像過度增強，並且能增強對比與細節，達到強化影像之目的。

關鍵字

對比強化 ； 直方圖均化 ； 影像強化 ； 影像融和

並列摘要

This paper presents an image enhancement approach based on histogram equalization (HE) and image fusion, which is abbreviated as IE/HEIF. The proposed IE/HEIF consists of three stages: First, obtain the complement of original image. Second, fuse the original image and its complement by linear interpolation and apply limited range histogram equalization to the fused image. Third, apply linear interpolation once more to fuse the original image and that obtained in the second stage. To improve the performance of IE/HEIF further, an adaptive scheme based on standard deviation of image blocks is employed for parameter adjustment in the linear interpolation. The approach is called IE/HEIF_std. By this doing, it is expected to have better image contrast and visual quality.
To justify the proposed approaches, several examples are provided in the simulation where comparisons with other HE-based approaches are made as well. The results indicate that both IE/HEIF and IE/HEIF_std are able to enhance image contrast and visual quality and better results are generally for IE/HEIF_std as expected. Moreover, the proposed IE/HEIF and IE/HEIF_std have better enhanced images than those HE-based approaches which suffer from over-enhancement and un-natural looking in the resulted images in general.

並列關鍵字

image fusion ； image enhancement ； contrast enhancement ； histogram equalization

參考文獻

[1] Mary Kim and Min Gyo Chung, “Recursively Separated and Weighted Histogram Equalization for Brightness Preservation and Contrast Enhancement,” IEEE Transactions on Consumer Electronics,” Vol. 54, No. 3, pp. 1389–1397, August 2008.

[2] Haidi Ibrahim, and Nicholas Sia Pik Kong, “Brightness Preserving Dynamic Histogram Equalization for Image Contrast Enhancement,” IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, pp. 1752–1758, November 2007.

[3] Chun-Ming Tsai and Zong-Mu Yeh, “Contrast Enhancement by Automatic and Parameter-Free Piecewise Linear Transformation for Color Images,” IEEE Transactions on Consumer Electronics, Vol. 54, No. 2, pp. 213–219, May 2008.

[4] Nyamlkhagva Sengee and Heung Kook Choi, “Brightness Preserving Weight Clustering Histogram Equalization,” IEEE Transactions on Consumer Electronics, Vol. 54, No. 3, pp. 1329–1337, August 2008.

[5] How-Lung Eng and Kai-Kuang Ma, ”A Dynamic Histogram Equalization for Image Contrast Enhancement,” IEEE Transactions on Consumer Electronics, Vol. 53, No. 2, pp. 593–600, May 2007.