How to calculate the radial void fraction of non spherical particles from in an image

How to calculate the radial void fraction of non spherical particles from in an image? I am attaching one such image from which I want to estimate the radial void fraction

Answer 1

[yanqi liu]

yes，sir，may be consider

clc; clear all; close all;
img = imread('https://ww2.mathworks.cn/matlabcentral/answers/uploaded_files/818369/Non%20spherical%20particle.PNG');
im = rgb2gray(img);
bw = im2bw(im);
bw = ~bw;
bw = imopen(bw, strel('disk', 2));
bw = imclose(bw, strel('disk', 19));
be = imbinarize(im,'adaptive','ForegroundPolarity','dark','Sensitivity',0.65);
be(~bw) = 0;
be2 = imerode(be, strel('disk', 2));
be(be2) = 0;
figure; imshow(img); hold on;
h = imshow(label2rgb(bwlabel(be), 'hsv'));
set(h, 'AlphaData', 0.7);

stats = regionprops(be, 'MajorAxisLength');
rate=mean(cat(1,stats.MajorAxisLength))

rate = 26.8974