农业工程学报2017，Vol.33Issue(18)：134-140,7.DOI:10.11975/j.issn.1002-6819.2017.18.018
像素自相关矩阵的阈值自适应角点检测算法
An adaptive threshold corner detection algorithm based on auto-correlation matrix of image pixel
摘要
Abstract
Harris algorithm is a classical corner detection algorithm.It can extract corners of image quickly and has a certain degree of anti-noise ability,but it has corner location error to some extent.It needs to artificially set 2 threshold parameters,and it can not easily eliminate false corners such as edge points,so it has somewhat lower accuracy of corner detection.For above-mentioned reasons,a modified Harris corner detection algorithm based on auto-correlation matrix of image pixel was proposed in this paper,and the purpose was not only to solve the problem of the variability and randomness of setting thresholds for corner response function (CRF) and non-maximum suppression in Harris algorithm,but also to improve the accuracy of corner location.In our paper,the most important innovation is embodied in 2 aspects:One is avoiding to set 2 thresholds of traditional Harris corner detection algorithm artificially,the other is locating corner more accurately by modified non-maximum suppression method.Firstly,original image was filtered by directional filtering and Gaussian low-pass filtering,and feature corner image was constructed by calculating determinant of every pixel's auto-correlation matrix.Potential corners of image could be heightened effectively,which had more significant intensity than other surrounding pixels,and could be recognized easily in feature corner image.Secondly,in order to improve intelligent level of the modified algorithm,we selected adaptive OTSU algorithm to determine segmentation threshold.The segmentation threshold of feature corner image could be calculated by OTSU algorithm,and the pre-selected regions were obtained.So the search range of corner detection was significantly decreased.On the basis,an optimized non-maximum suppression method was adopted in our research,which could divide each pre-selected region into several 3×3 square subranges,and correct corners were extracted from potential corners of each square subrange,false corners were eliminated effectively.Finally,in order to validate the efficiency and reliability of the modified algorithm,5 groups of comparison experiments were performed in our research.Five images,including generic image format (jpg,bmp),and multi-band remote sensing image format (GF-2 data),were selected to test performance of the modified algorithm and Harris algorithm,which contained the total of detection corners,the number of correct corners,the number of false corners,the number of omissive corners,and the detection rate of correct corners.According 5 groups of comparison experiments,the accuracy of corner detection in different types of images is improved,for crop vegetation remote sensing image,the accuracy of corner detection is improved by 27.06 percentage points.We can draw a conclusion that the improved algorithm can not only calculate the optimal threshold automatically,but also locate the corners more accurately.Therefore,our modified algorithm can greatly improve the precision of corner detection.The proposed algorithm is more accurate and efficient than traditional algorithm,its adaptive characteristic makes it easy to be integrated in an image processing system or image registration module,and it has higher feasibility and application value.Experiments also show that there is some insufficiency to be improved in our research,for example,some corners in picture of cubes could not be detected correctly with either our modified algorithm or Harris algorithm.In our future research,we propose to partition an image into several sub-image blocks,and independently determine each sub-image block's segmentation threshold by OTSU algorithm,so that the corners not prominent in full image can be significantly strengthened in sub-image blocks,and can be detected correctly.The research could provide reference for agricultural remote sensing image data detection.关键词
图像处理/算法/角点检测/自相关矩阵/特征角点图像/非极大值抑制Key words
image processing/algorithms/corner detection/auto-correlation matrix/feature corner image/non-maximum suppression分类
信息技术与安全科学引用本文复制引用
邓小炼,杜玉琪,王长耀,王晓花..像素自相关矩阵的阈值自适应角点检测算法[J].农业工程学报,2017,33(18):134-140,7.基金项目
遥感科学国家重点实验室课题(Y6Y00200KZ) （Y6Y00200KZ）
