摘要
针对海底侧扫声纳图像对比度低、纹理弱、噪声严重等问题,提出了一种基于第二代Curvelet变换的声纳图像增强算法。首先对原始声纳图像进行多尺度、多方向的Curvelet变换分解,得到低频子带和高频子带;然后引入非线性S型函数对低频系数进行处理,提高图像整体的对比度;采用一种可以避免过度增强的新型非线性函数对各尺度的高频子带系数进行处理,提高图像整体的对比度,增强图像边缘和纹理细节,并通过估计噪声水平设定阈值进行阈值降噪。最后经Curvelet逆变换得到增强图像。实验表明,该方法不仅改善了海底侧扫声纳图像对比度低的问题,而且降低了噪声,突出了声纳图像的边缘和纹理细节。
Considering the low contrast,weak texture and strong noise of side-scan sonar image,a sonar image enhancement algorithm based on the second generation Curvelet transform is proposed.Firstly,the original sonar image is decomposed at different scales and directions by Curvelet transform to obtain the low frequency subband coefficients and the high frequency subband coefficients.And then the Sigmoid function is applied to deal with the low frequency subband coefficients,so as to enhance the global contrast of the images.A new nonlinear function is also used to process the high frequency subband coefficients,which aims at highlighting the edge and texture details of the image.The noise threshold is chosen by estimating the noise levels and used to de-noise.Finally,the enhanced sonar image is obtained by the inverse Curvelet transform.Experimental results show that the enhancement method proposed in this paper can not only enhance the contrast of the sonar image and reduce the noises of the image,but also can highlight the edge and texture details of the sonar image.
出处
《海洋测绘》
2012年第1期8-10,17,共4页
Hydrographic Surveying and Charting
基金
国家自然科学基金项目(60972101)
