How to store information about material porosity?

Hello everyone,

I am currently reviewing the porosity levels of some CT scans (985422 in total). Since we only got a readonly version of the images we had to improvise a subroutine for counting the void level in the material (black pixel). With a for loop I wanted to store the value in a matrix and plot them as the following cutout shows:

Matrix overview

x-axis 1st y-axis 2nd y-axis 3rd y-axis

column 1 column 2 (blackpixel_percentage) column 3 (white_percentage) void growth factor

0.04 value 1 value 1 value 1 = values(column2) / values(column3)

0.08 value 2 value 2 value 2 = values(column2) / values(column3)

0.12 value 3 value 3 value 3 = values(column2) / values(column3)

With this I am facing some problems:

a.) Since the desired white and black values are being overwritten in the loop, I have no idea how to properly store them in a matrix. I tried using the CT_scan_num variable, but it does not work in the loop.

b.) I am not sure how to plot one x axis and three y axis. I would need this setup in order to obtain a "control graph" for additional scans

for CT_scan_num = 0000:0003
     CT_index = sprintf('%04d',CT_scan_num);
     CT = 'CT';
     ind3_format = '.bmp';
     ind_name = [CT CT_index ind3_format];
     i=imread(ind_name);
     %imshow(i);
     %Image Adjust
     adj=imadjust(i,stretchlim(i));
     % imshow(adj);
     %Convert RGB to Gray
     gry=rgb2gray(adj);
     % imshow(gry,[]);
     %Image segementation by thresholding
     level = 0.45;
     thres=im2bw(gry,level);
     % imshow(thres);
     % Image morphological operation
     bw=bwmorph(thres,'clean',20);
     % imshow(bw);
     %End
     black = length(find(bw==0));
     white = length(find(bw==1));
     
     % a.) Porosity (void level)
     blackpixel_percentage = (black/(black+white))*100;
     
     % b.) Material content (matrix level)
     white_percentage = (white/(black+white))*100;
     
     % c.)increment of the CT images (distance where image plane was cutted
     % out = from 0 to 3
       i_CT = 0.04
end

Best Regards