Integers can only be combined with integers of the same class, or scalar doubles.

 mask = 1-double(im2bw(gray, graythresh(gray)));
 strel = [0 1 1 1 0; 1 1 1 1 1; 1 1 1 1 1; 1 1 1 1 1; 0 1 1 1 0];%structuring element
  shadowavg_red = sum(sum(image(:,:,1).*shadow_core)) / sum(sum(shadow_core));

[Walter Roberson]

You need to stop tagging your questions as Urgent. We typically close or delete "Urgent" questions.

http://www.mathworks.com/matlabcentral/answers/29922-why-your-question-is-not-urgent-or-an-emergency

[charuleelaa vanilavarasu]

Okay! sorry!

Answer 1

[Walter Roberson]

Whatever your shadow_core is, it is double precision, but your image variable is integer data type.

    shadowavg_red = sum(sum(double(ImageArray(:,:,1)).*shadow_core)) / sum(sum(shadow_core));

or better yet,

mean(ImageArray(logical(shadow_core)))

Note the renaming of image to ImageArray. Using a variable named "image" always leads to problems.