Research On Image Recognition And Measurement Method Of Building Cracks

Crack is a common and important disease in building construction and it is of great significance for structural inspection,identification and maintenance of dangerous buildings to detect.With the help of digital image processing technology and computer vision technology,the recognition algorithm,crack image calibration method and crack parameter calculation method of building construction crack image are researched,and the building of on-site crack measurement system is realized,which can provide a lot of reference data for housing quality inspection and evaluation.The main research contributions in this paper are as follows.(1)The overall process of digital image processing technology applied to the image recognition of cracks in buildings is proposed.Through the processing steps of graying,median filtering,maximum entropy threshold segmentation,information screening and crack connection on the collected crack images,the black-and-white binary image containing only crack targets and background can be obtained.(2)An information screening method based on binary image is proposed.On the basis of the target segmentation,the morphological processing is used to preliminarily screen the binary image of cracks,filter out small areas of noise and close small cracks.Combined with the characteristics of connected domains such as the ratio between long and short axes and area,the interference information is eliminated.A crack fracture connection algorithm based on convex hull model in computational geometry is proposed.When the distance between the fracture point is small,good recovery results can be obtained by using a straight line fitting method.(3)Because of the stable identification and positioning function of the two-dimensional bar code,QR code is used as the crack observation point to arrange on the building surface,so that the problem of crack numbering in images can be resolved.A pixel calibration method based on two-dimensional code is proposed.By using the position detection graphic feature of two-dimensional code,the calculation of the conversion ratio is achieved under the pinhole imaging model,which can obtain the conversion relationship between the pixel size and the physical size.Experiments of QR code image calibration show that the calibration results are satisfactory when the distance is appropriate and the camera plane is substantially parallel to the crack,and recognition deficiencies in common targets are addressed.(4)A method for calculating crack parameters based on digital image processing is proposed in this paper,named the "expanded circle method".This method can extract parameters from the binary image of cracks and convert the crack information from image format to data format.The effectiveness and stability of the algorithm are verified through laboratory simulated crack experiments,and quantitative identification of cracks is achieved.The proposed method makes up for the shortcomings of incomplete information and the difficulty of obtaining the specific location width of the crack about the existing crack parameter calculation methods.(5)The building crack image detection system is built.By designing MATLAB-based computing programs and operating interfaces,the operability of using digital image processing technology to identify and measure cracks in buildings is improved.The field crack width measurement experiment based on the feasibility of the system illustrate the validity of the proposed method,which offers a new tool for practical application in the crack detection of building construction.