玉米冠层平行多目图像匹配方法

    Matching method of parallel multi-ocular image for corn canopy

    • 摘要: 针对一种四通道矩形排列的多光谱相机,开发了一种平行多目成像匹配模型。利用相机拍摄了田间玉米冠层图像,相机的4个通道分别为R(红)、G(绿)、B(蓝)和NIR(近红外),拍摄距离为0.5 m左右。分析了玉米冠层图像的特点,提出了一种图像匹配方法。该方法首先选择某一通道图像作为源图像,其他通道图像作为目标图像,源图像中叶片边缘作为源特征点,由该点18个方向的导数作分量构成特征向量。其次在目标图像中搜索相应的目标特征点,若在其中某一区域内的点与源特征点所在边缘方向夹角小于某阈值,将特征向量与源特征向量的距离为最小的点视为匹配的目标特征点,构成特征点对集合。对于该点对集合中每5对不共线特征点构造1个仿射变换,对所有仿射变换取平均值,构成从目标图像到源图像的仿射变换,完成图像匹配。该方法适用于不规则目标物,复杂背景,且目标物在不同通道中变化较大的情况,算法原理简单,实现容易。

       

      Abstract: A image matching model of parallel multi-ocular is introduced. The camera is rectangle arranged four channel multi-spectral camera, the four channels is R, G, B and NIR respectively. The corn canopy images in field are captured by the camera, and the distance between the camera and the corn canopy is about 0.5 m. The features of the images are analysed, and a new matching method of images is proposed. One channel image act as source, others as destination, and the edge points of the corn leaf in source image are source feature points, feature vector of each point is composed by 18 directional derivatives. After that, the destination feature point is searched in destination image. In a local area of destination image, if the intersection angle of edges that point and source point located is smaller than one threshold, and the distance between feature vector of the point and source feature vector is minimum among all of them, then the point is matched destination feature point, and the feature points pair set is constructed. Each five non-co-linear feature point’s pair in above set can construct one affine transform. Averaging all such affine transforms, the affine transform from destination image to source image is constructed, and the match of two images is finished. This method is suitable for irregular object, complicated background, and the object change a lot in different channel.

       

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