How to get a particular histogram from an image

Good evening,

for a given image, I should obtain a histogram on all 255 gray levels, as shown in figure, and it must be scaled linearly between minimum and maximum :

Thanks in advance.

[Adam]

Isn't that already scaled linearly between the min and max?

[gae mast]

I have another image and I want to obtain this type of histogram, do you help me?

[Adam]

doc imhist

[gae mast]

Yes, I know imhist but I must modify histogram of my image to obtain histogram similiar to that in figure, how do it?