用水线阈值法分割图像 对矩阵进行四叉树分解 将图像分为文字和非文字的两个类别 形态学梯度检测二值图像的边缘-Water line image thresholding segmentation of matrix quadtree decomposition of the image into text and non-text for these two types of morphological gradient detected binary image of the edge