受光照条件和噪声影响, 采用摄像方法检测裂缝时, 常用的边缘提取算法适用性较差。为此, 提出累积梯度算法用于计算裂缝边界。首先采用自适应二值化方法和图像形态学操作得到掩模图像。将掩模图像作用于原始图像, 得到扩充的裂缝区域图像。对该图像进行迭代膨胀, 对图像灰度值相加得到累积灰度值, 再用膨胀前后2幅图像的累积灰度值相减其差值最大时为累积梯度, 并将膨胀前的图像作为提取的裂缝。实验结果表明该方法能够在复杂背景下提取得到裂缝。

Edge extraction algorithms in digital image processing are often noise sensitive in detecting building cracks due to un-uniform illumination and the surounding affects. An accumulated gradient algorithm was presented to calculate the crack boundary. An adaptive binarization algorithm and morphology operations were adopted to obtain an image mask firstly. The mask image was acted on the original image to obtain the expanded image of the crack area. Then the image was iteratively expanded, and the gray value of the image was added to obtain the cumulative gray value.The accumulated gray between two successive images before and after expansion were subtracted, and the maximum difference was the cumulative gradient, the image before expansion was considered as the extracted crack. Experimental results show the crack can be extracted by this algorithm in complex backgrounds.