基于四通道不可分提升小波的多聚焦图像融合

Multi-focus image fusion based on four-channel non-separable lifting wavelet

张量积小波及其提升小波只强调图像的水平方向和垂直方向的边缘,造成其在应用于多聚焦图像融合时结果图像的空间分辨率不高;而二维四通道不可分小波对图像进行融合时虽有较高的空间分辨率,但由于对图像进行分解和重构时采用了卷积运算,使得融合方法的运算量增大。针对上述问题,把二维四通道不可分小波滤波器组进行提升分解,并提出了一种基于此提升分解方案的多聚焦图像融合方法。首先,对二维四通道不可分小波滤波器组的多相位矩阵进行提升分解,并利用所得提升方案对源图像进行分解;其次,对分解后的低频子图像和高频子图像分别进行融合,得到融合金字塔;最后,做二维提升小波逆变换,得到融合后图像。利用熵、平均梯度和清晰度等客观指标对融合结果进行评价。实验结果显示,所建议提升小波融合方法比张量积小波和张量积提升小波融合方法及轮廓波融合方法有较高的清晰度,比提升之前的二维四通道不可分小波融合方法速度有了较大提升。

Tensor product wavelet and its lifting wavelet only emphasize the horizontal and vertical edges of images. This makes the spatial resolution of the fused image lower when these two kinds of wavelet are applied to multi-focus image fusion. The image fusion method based on two-dimensional four-channel non-separable wavelet has high spatial resolution, but the computation amount of this fusion method is higher since the convo- lution operation is adopted while the images are decomposed and reconstructed. To solve these problems, this paper lifts two- dimensional four-channel nonseparable wavelet filter banks and proposes a new method of multi- focus image fusion based on this lifting schema. Firstly, the polyphase matrix of the two-dimensional four-chan- nel non-separable wavelet transform is factorized into the lifting format and the multi-resolution analysis of the original images is performed. Secondly, the low frequency sub-images and high frequency sub-images are fused respectively. Finally, the inverse transform of the lifting wavelet is implemented and the fused image is ob- tained. The fusion performance is evaluated by entropy, average gradient and image definition. The experimen- tal results show that the proposed fusion method has higher definition and spatial resolution than that of the ten- sor product wavelet method, tensor product lifting wavelet method, and contourlet fusion method. The speed of the proposed fusion method has been greatly improved than that of its original two-dimensional four-channel non-separable wavelet fusion method.