通过iTEM图像处理软件，可以将金相图片进行标尺变换，使其名义放大倍率满足标准要求。利用iTEM软件测量功能，在图片上做一圆周，软件会自动计算出其在标准倍率下的面积。点击其中的点计数测量选项，可以快速计算出圆周内部以及与圆相交的晶粒数，从而得出单位面积内的晶粒数。再按照ASTM E112-2013中的晶粒级别指数定义公式，就可以计算出试样的晶粒级别指数。测定结果表明：采用iTEM软件计算的晶粒级别指数与试样的标准值符合良好。

By using iTEM image processing software, the scale of the metallographic picture can be changed to make the nominal magnification of the image meet the standard requirements. By using the measurement function of iTEM software, a circle can be made in the picture, and then the software will automatically calculate the area of the circle under the standard magnification. By clicking on the point count measurement options, the number of grains inside the circle and intercrossed with the circle can be calculated quickly respectively, and then the number of grains per unit area can be obtained. Then according to the standard of ASTM E112-2013 in which the grain size number is defined, the grain size number of the sample can be calculated. The results show that the grain size number calculated by using iTEM software was in good agreement with the standard values of the sample.