bp1
finding differences in images
Contents
read images
% original images m1 = imread('corV0001.bmp'); m2 = imread('corV0002.bmp'); subplot(2,1,1); imshow(m1); subplot(2,1,2); imshow(m2); disp('image size'); disp(size(m1));
image size 240 320 3
convert to grayscale and find differences
close all g1 = im2double(rgb2gray(m1)); g2 = im2double(rgb2gray(m2)); d = g2 - g1; dmax = max(max(d)); dmin = min(min(d)); fprintf('max diff %g\nmin diff %g\n',dmax,dmin);
max diff 0.556863 min diff -0.509804
show differences
One way of illustrating differences is to map the image range -1 .. 1 into 0 .. 1 by (1+diff)/2
cdiff = (1+d)/2; imshow(cdiff);
difference histogram
% zero difference corresponds to 0.5 brightness
imhist(cdiff);
% alternative plot [counts,x] = imhist(cdiff); counts(129)=0; % don't count zero differences stem(x-0.5,counts,'.');
color difference display
red is positive difference, blue is negative difference
% black background bipolar_image(d,1);
% white background bipolar_image(d,2);
% superimpose on image
thres = 0.15*max(dmax,-dmin);
k1 = d < -thres;
k2 = d > thres;
g = (g1.*not(k1)).*not(k2);
final = cat(3,g+double(k2),g,g+double(k1));
imshow(final);
