说明：  图像预处理、灰度化，直方图均衡化，图像去噪，阈值分割，边缘检测，形态学处理等及计算裂纹图像的周长和面积
(Image pre processing, grayscale, histogram equalization, image denoising, threshold segmentation, edge detection, morphological processing and calculation the perimeter and area of crack image)