How to create a grid of squares inside a circle, assign them and get the sum of pixels inside the squares?

Hello fellows. I want to create a grid of squares within a circle like the image attached. The condition is to consider only total squares as the image, assign them, and get the sum of pixels within each square. I want to overlay this circle with the grids in a gray image. I have the following code to build the circle mask:

 if true
%build circular mask
clearvars Mask BW H x_center y_center
data = imread(whateverimage);
x_center = fix(size(data,1)/2);
y_center = fix(size(data,2)/2);
H = imellipse(gca, [ 16  17 90.2 90.2 ] )
wait(H);
BW = createMask(H);
Mask(:,:,1)=BW;
I1=single(data).*Mask;
figure(3), imshow(I1(:,:,1),'DisplayRange', [],'InitialMagnification', 'fit');
  end

The circle ROI is fine. I'm stuck with this grid in how to fit it inside the circle ROI and quantify inside the squares.

Thanks in advance. Best regards.

[Image Analyst]

I don't see any attached image.

Answer 1

[KSSV]

[X,Y,Z] = peaks(500) ;
% center of circle and Radius 
C = [mean(unique(X)) mean(unique(Y))  ] ;
R = 1.5 ;
% make circle 
th = linspace(0,2*pi,500) ;
xc = C(1)+R*cos(th) ; yc = C(2)+R*sin(th) ;
% get pixels inside circle 
idx = inpolygon(X(:),Y(:),xc,yc) ;
Z(~idx) = NaN ;
iwant = nansum(Z(~idx))
figure
hold on
pcolor(X,Y,Z) ;
shading interp ;