deriv

Contents

open file

clear
close all
filename = '2015-01-26_18-00-42.JPG';
rgb = imread(filename);

crop

% [rgbc rect] = imcrop();
rect = [2138 782 1396 884];
rgbc = imcrop(rgb,rect);
imshow(rgbc);
g = rgb2gray(rgbc);
im = im2double(g);
clear rgb g
zm = 0.5;

Warning: Image is too big to fit on screen;
displaying at 67% 

first moments

m0 = [ 1 2 1; 2 4 2; 1 2 1];
m1 = [ -1 0 1; -2 0 2; -1 0 1];
m2 = [ -1 -2 -1; 0 0 0; 1 2 1];
a0 = imfilter(im,m0);
a1 = imfilter(im,m1);
a2 = imfilter(im,m2);
slope = sqrt(a1.^2 + a2.^2);
gmax1 = max(max(slope));
slope = slope/gmax1;
imshow(2*slope);

Warning: Image is too big to fit on screen;
displaying at 67% 

second moments

b11 = imfilter(a1,m1);
b22 = imfilter(a2,m2);
b12 = imfilter(a1,m2);
b21 = imfilter(a2,m1);
br = (b11+b22)/2;
dmax = max(max(br));
dmin = min(min(br));
gmax2 = max(dmax,-dmin);
bipolar_image(2*br/gmax2);

Warning: Image is too big to fit on screen;
displaying at 67% 

expand laplacian

corner operator

bc = (b11-b22);
bs = 2*b12;
ac = a1.^2 - a2.^2;
as = 2*a1.*a2;
e = bc.*as-bs.*ac;

dmax = max(max(e));
dmin = min(min(e));
gmax3 = max(dmax,-dmin);
bipolar_image(e/gmax3);

Warning: Image is too big to fit on screen;
displaying at 67% 

expand corner metric

superimpose corners on image

bipolar_image(e/gmax3,im,0.1);

Warning: Image is too big to fit on screen;
displaying at 67% 

expand superimposed corner metric

show strongest corners

thresh = 0.2;
BW = e > thresh*gmax3;
fprintf('count %d\n',sum(sum(BW)));
%imshow(~BW);
bipolar_image(BW,im,thresh);

count 431
Warning: Image is too big to fit on screen;
displaying at 67% 

expanded strong corners

deriv matrix

----------------
| a0 | ax | as |
----------------
| ay | br | bs |
----------------
| ac | bc | e  |
----------------

[r c] = size(im);
data = ones(3*r,3*c);
ri = 1:r;
ci = 1:c;
% column 1
data(ri,ci)=a0/16;
data(r+ri,ci)=(a2/3+1)/2;
data(2*r+ri,ci)=(ac/9+1)/2;
% column 2
data(ri,c+ci)=(a1/3+1)/2;
data(r+ri,c+ci)=(br/12+1)/2;
data(2*r+ri,c+ci)=(bc/12+1)/2;
% column 3
data(ri,2*c+ci)=(as/9+1)/2;
data(r+ri,2*c+ci)=(bs/12+1)/2;
data(2*r+ri,2*c+ci)=abs(e/20);

imshow(imresize(data,1/3));

Warning: Image is too big to fit on screen;
displaying at 67% 

Published with MATLAB® R2014a