Using c$++,$ design a function for statistical analysis of an image, which evaluates and returns min, max, mean, standard deviation, variance, and SNR $($signal$-$to$-$noise ratio$)$ of a gray$-$scale image. This function shall use an array containing an image as a single argument.

Also design a function, which evaluates, returns and plots a histogram of a gray$-$scale image. This function shall use an array containing an image as a single argument.