求翻译：当其不为零时，表示像元点与其邻域灰度有变化，存在边缘；其值越大，对应图像该点的边缘就越清晰，图像对比度就越好；而在灰度均匀区域，则 。是什么意思？

When its non-zero grayscale pixel point and its neighborhood changes, the existence of the edge; the greater its value, corresponding to the edge of the image of the point more clearly, the better the image contrast; in gray uniform region, is.

When it is not zero, it indicates a point $domain with its neighbors gray there is a change, there is edge; the larger the value, the corresponding image on the edge of the sharper contrast in the image, the better, and even in the gray zone, then.

正在翻译，请等待...

When it is not zero, represents a pixel neighborhood gray level changes, edge; the larger its value, corresponds to the point on the edge of the image more clear, the better image contrast; in gray uniform area that is.

When it is not the zero hour, if indicates element the neighborhood gradation to have the change, has the edge; Its value is bigger, corresponding image this edge is clearer, the image contrast gradient is better; But in gradation homogeneity rangee, then.