基于NSST的遙感圖像增強算法研究
本文選題:遙感圖像 + 圖像增強; 參考:《新疆大學(xué)》2017年碩士論文
【摘要】:遙感圖像作為人們對地球進行研究和監(jiān)測的一個重要的依據(jù),起到十分重要的作用。遙感已經(jīng)從軍事領(lǐng)域轉(zhuǎn)向了民用方面,由此使其發(fā)展的更加迅速。但是遙感圖像在獲取和傳輸?shù)倪^程中,受到很多因素的影響,如傳感器、大氣等,使得到的遙感圖像變得失真、模糊、對比度低等。為了便于研究人員對遙感圖像的識別,就必須對遙感圖像進行處理。圖像增強是一種圖像處理方法,主要是針對圖像中的一些有用信息進行突出或強化。因此,圖像增強對遙感圖像的識別是必不可少的。本文針對遙感圖像存在的低對比度、低信噪比、邊緣保持較弱、細節(jié)丟失等問題,提出了兩種新的圖像增強算法。其中一種是基于在NSST域的自適應(yīng)閾值和引導(dǎo)濾波相結(jié)合的遙感圖像增強算法。引導(dǎo)濾波是一種圖像濾波算法,具有良好的平滑能力的同時還能對圖像邊緣梯度能很好的保持,得到了研究人員的關(guān)注。鑒于這些特性,本文將結(jié)合引導(dǎo)濾波對圖像的細節(jié)和邊緣部分進行增強。首先,該算法通過對待處理的圖像進行NSST分解,將圖像分解成為一個低頻部分和若干個高頻部分。然后,采用線性變換對低頻部分進行線性拉伸,目的在于對比度的改變;高頻部分,進行抑制噪聲處理,將采用自適應(yīng)閾值法,其次再進行引導(dǎo)濾波增強圖像的細節(jié)部分和邊緣梯度。最后,將處理后低頻和高頻部分進行重構(gòu)處理,得到增強后的圖像。通過實驗表明,該算法對遙感圖像的視覺效果得到了改善,客觀指標(biāo)上與對比算法相比,信息熵、峰值信噪比和結(jié)構(gòu)相似度有了一定的提升。本文另外一種是基于NSST域的直方圖均衡和引導(dǎo)濾波相結(jié)合的遙感圖像增強算法。直方圖均衡是一種經(jīng)典的用來提高對比度的算法,本文用它來對圖像進行預(yù)處理,提高圖像整體的對比度。經(jīng)過NSST分解后的低頻部分的處理與上一種算法一樣采用線性變換的方式,高頻部分的去噪處理采用閾值去噪的方法,對于圖像的細節(jié)部分和邊緣,還是采用引導(dǎo)濾波的方法。實驗表明,與對比算法相比較,該算法明顯地提升了圖像的對比度,增強了圖像的細節(jié)和邊緣梯度能力。
[Abstract]:Remote sensing image plays an important role as an important basis for people to study and monitor the earth. Remote sensing has shifted from military to civilian, thus making its development more rapid. However, in the process of obtaining and transmitting remote sensing image, it is affected by many factors, such as sensor, atmosphere and so on, which make the remote sensing image become distorted, blurred and low contrast. In order to facilitate the recognition of remote sensing images, remote sensing images must be processed. Image enhancement is an image processing method, which is mainly used to highlight or enhance some useful information in the image. Therefore, image enhancement is essential for remote sensing image recognition. In this paper, two new image enhancement algorithms are proposed to solve the problems of low contrast, low signal-to-noise ratio (SNR), weak edge retention and detail loss in remote sensing images. One is a remote sensing image enhancement algorithm based on adaptive threshold and guided filtering in NSST domain. The guided filter is a kind of image filtering algorithm, which has good smoothing ability and can keep the edge gradient of the image well, which has been paid attention to by researchers. In view of these features, this paper will enhance the details and edges of the image in combination with bootstrap filtering. Firstly, the algorithm decomposes the image into a low frequency part and several high frequency parts by NSST decomposition. Then, the low frequency part is stretched linearly by linear transformation to change the contrast, and the high frequency part, which is used to suppress noise, will adopt the adaptive threshold method. Secondly, the detail part and edge gradient of the image are enhanced by guided filtering. Finally, the processed low frequency and high frequency parts are reconstructed to get the enhanced image. The experiments show that the visual effect of the algorithm is improved, and the information entropy, peak signal-to-noise ratio and structural similarity are improved compared with the contrast algorithm. The other one is a remote sensing image enhancement algorithm based on histogram equalization and guided filtering in NSST domain. Histogram equalization is a classical algorithm to improve the contrast. In this paper, we use it to preprocess the image to improve the overall contrast of the image. The processing of the low-frequency part after NSST decomposition is the same as that of the previous algorithm. The high-frequency part is de-noised by the threshold denoising method, and the image details and edges are still processed by the guided filtering method. The experimental results show that compared with the contrast algorithm, the algorithm improves the contrast of the image, and enhances the ability of image detail and edge gradient.
【學(xué)位授予單位】:新疆大學(xué)
【學(xué)位級別】:碩士
【學(xué)位授予年份】:2017
【分類號】:TP751
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