用来计算四杆机构的运动分析，避免了过多的角度象限的讨论-Used to calculate the movement of four-bar linkage analysis, to avoid too much discussion of the point of view of quadrant

this function is getting the background by mean function for rael time . the function calc the mean of every pixel .

matlab环境下的计算器程序，简易计算器！-Matlab environment the calculator program, simple calculator!