*3.1. Global Thresholding*

The most basic and at the same time least complicated method of crack segmentation is the global thresholding [54–56]. It consists of determining for the whole analyzed image the global threshold value on the histogram, below which all pixels are interpreted as cracks and the rest are treated as background. This method is the least accurate of all methods of image analysis, because it can result in a very noisy image—cracks are very often integrated into the noise generated by the background. Depending on the complexity of the morphology of the analyzed surface, very often such an image is not suitable for analysis and drawing conclusions in terms of identification and evaluation of the cracking patterns. Currently, no analysis is performed using the global thresholding method, while the thresholding operation itself is popularly used at various stages of analysis, especially at an image pre-processing stage.
