How to get average intensity from a selected image window

Hi everyone,

I have got the intensity value like below from the selected image window.

   66   61   54
   65   59   55
   60   54   60

How can I get the average of this numbers.

Any advice?

Thanks

Answer 1

[Guillaume]

First of all, usually x is used to refer to the horizontal dimension and y to the vertical one. That's the 2nd and 1st dimension of your matrix respectively. So to access pixel (x, y), you need to do:

value = I(y, x);

Because of that, I usually don't use x and y as a variable, but row and col.

Secondly, to access a rectangle of pixels, don't use a loop (particularly as you keep overwriting the scalar value), but just use matrix indexing:

values = I(y-g:y+g, x-g:x+g)

Finally to get the average of all values in a matrix:

meanvalues = mean(values(:));

[Tania]

Excellent, Works perfect

Answer 2

[Abdullah]

How to let x and y read the row and column ?