求翻译：即梯度均值可以近似地表示出该相邻图像区域的灰度变化程度，也即该区域的边缘的多少及边缘的清晰程度。将各个相邻图像区域的平均梯度幅值求和，则可表征整幅图像的对比度。是什么意思？

The gradient of the mean can be approximated expressed the adjacent area of ​​the image gray-scale changes in the degree of the edge of the region and the edge of clarity. Each adjacent image area, the average gradient amplitude sum, you can characterize the entire image contrast.

The gradient values can be similar to that of the adjacent area of the image gray, extent of the changes is that the region is also the number of edges and edge the clarity. The adjacent area of the image in the average gradient values, you can table the whole image contrast.

正在翻译，请等待...

Gradient value can approximate representation of the gray-scale variability of adjacent image area, that is, how much of the edge of the area and edge clarity. Average gradient amplitude summing adjacent to each area of the image, you can characterize the entire image contrast.

Namely the gradient average value may approximately express this neighboring image region gradation change degree, also namely this region edge how many and edge readability.Each neighboring image region average gradient peak-to-peak value summation, then may attribute the entire image the contrast