How can I findout mean,standard deviation and variance using hiatogram of an image

I have an image of 256X256. I constructed histogram for that image. Now I want extract parameters(mean, standard deviation and variance) using the histogram. Can anyone help. Thanks in advance

[Jan]

It depends on what "constructed histogram" eactly means. Is this available as diagram, vector, printed on paper or an image file? As far as this detailed is clear, it does not matter if the original data belong to an image or a set of stock prices.

Answer 1

[Iain]

Easier to do that straight from the image:

 my_image = uint16(randn(128,128)*16383);
 std_of_my_image = double(std(my_image(:)));
 var_of_my_image = std_of_my_image^2;
 mean_of_my_image = mean(my_image(:));