A mine low illumination image enhancement algorithm
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摘要: 针对小波变换在图像边缘保持和细节处理方面无法保持平衡及多尺度Retinex算法易造成图像出现光晕伪影和噪声污染严重等问题,将小波变换与基于多尺度引导滤波的多尺度Retinex算法相结合,提出了一种矿井低照度图像增强算法。该算法首先将低照度图像进行小波分解得到高频分量和低频分量;然后对图像高频分量采用三段式阈值函数进行小波去噪,对图像低频分量采用非线性全局亮度校正以增强图像亮度,同时采用多尺度引导滤波函数代替传统多尺度Retinex算法的高斯滤波函数来估计照射分量,进而求取反射分量,并运用主成分分析法对反射分量与非线性全局亮度校正的图像进行融合,有效提升图像边缘细节保持效果;最后对图像高频分量和低频分量进行小波重构,并对小波重构后的图像进行非线性变换,解决图像泛灰问题。实验结果表明,该算法具有很强的噪声抑制能力,可有效提升图像亮度和对比度,使图像边缘保持性能和细节信息丰富度得到有效平衡,避免了图像出现光晕伪影、颜色失真等现象。Abstract: The wavelet transform cannot maintain a balance in image edge preservation and detail processing and the multi-scale Retinex algorithm is prone to halo artifacts and serious noise pollution in images. In order to solve the above problems, a mine low illumination image enhancement algorithm is proposed by combining the wavelet transform with the multi-scale Retinex algorithm based on multi-scale guided filtering. Firstly, the algorithm decomposes the low illumination image into wavelets to obtain the high-frequency and low-frequency components. Secondly, the wavelet denoising is applied to the high-frequency components of the image using a three-stage threshold function, and nonlinear global luminance correction is applied to the low-frequency components of the image to enhance the image luminance. Moreover, the multi-scale guided filter function is used to estimate the illumination components instead of the Gaussian filter function of the traditional multi-scale Retinex algorithm, and then the reflection components are obtained. The principal component analysis method is used to fuse the reflection component and the non-linear global luminance correction image so as to improve image edge detail preservation effect effectively. Finally, the wavelet reconstruction is performed on the high-frequency components and low-frequency components of the image, and the wavelet reconstructed image is nonlinearly transformed to solve the image graying problem. The experimental results show that the algorithm has strong noise suppression capability, can improve the image luminance and contrast effectively, make the image edge preservation performance and detail information richness effectively balanced, and avoid the image halo artifacts and color distortion.
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