| Researcher | Methods | Objectives of the methods |
| Ying and Salari (2010) [9] | Beamlet Transforms (BT) | Extraction of curvilinear features of crack from pavement images. |
| Hough (1962) [10] | Hough Transform (HT) | Recognize complex pattern in a picture. |
| Leymarie and Levine (1992) [11] | Grassfire Transform (GT) | Describe planer object shape including region and boundary features. |
| Canny (1986) [12] | Laplacian of Gaussian (LOG) operator | For edge detection. |
| Witkin (1984) [13] | Scale-space filtering | Precisely localize a large-scale structure using the gaussian convolution. |
| Sobel [14] | Sobel operator | The pixel-level edge detection algorithm. |
| Pallotta (2014) [15] | Zernike moments operator | Compute all the edge parameters for subpixel detection. |
| Ying-Dong et al. (2005) [16] | Sobel-Zernike moments operator | A fast subpixel edge detection method. |
| Dong, W (2008) [17] | Prewitt method | Wall crack assessment from image. |
| Jianzhuang et al. (1991) [18] | Otsu method | Classify the image into background and foreground and find the threshold value to minimize the variances. |
| Farhidzadeh et al. (2013) [19] | fractal method | Reinforcement concrete damage assessment. |
| Massaro, E., & Bagnoli, F. (2014) [20] | Percolation method | Large-size concrete surface crack detection method [21] - [32] . |
| Pudney (1998) [33] | Distance-ordered homotopic thinning (DOHT) | Distance-ordered homotopic thinning (DOHT) is effective and efficient Skeletonization Algorithm to verify a real and synthetic 3D image. |
| Fortune, S. (1987) [34] | Voronoi diagram | Exact shape analysis and accurate skeleton approximation. |
| Choi et al. (2003) [35] | Euclidean skeleton | Efficient and accurate skeletonization method. |
| Jia and Tang (2003) [36] | ND tensor voting | Can apply roughly homogenous and periodic textures images. |