cohist session 2

filename = 'flowers4.png';
% filename = 'color_cube.jpg';
rgb = imread(filename);
rgb = im2double(rgb);
imshow(rgb);

uncomment for interactive specification get sample of background color

% [samp rect] = imcrop;
% save sess2 samp rect
load sess2
imshow(samp);

xc = samp(:,:,1) - 0.5*(samp(:,:,2)+samp(:,:,3));
yc = sqrt(3)/2*(samp(:,:,2)-samp(:,:,3));
zc = (samp(:,:,1)+samp(:,:,2)+samp(:,:,3))/3;
subplot(2,2,1);
imshow(samp);
subplot(2,2,2)
cohist((xc+1)/2,(yc+1)/2);
xlabel('chroma x');
ylabel('chroma y');
subplot(2,2,3);
cohist(zc,(xc+1)/2);
xlabel('value');
ylabel('chroma x');
subplot(2,2,4);
cohist(zc,(yc+1)/2);
xlabel('value');
ylabel('chroma y');

close
hist = imhist((xc+1)/2);
% y = func1(hist);
sx = sort(xc(:));
y(1) = sx(10);
y(2) = sx(end-9);
fprintf('chroma x range: %g %g\n',y);
xd = rgb(:,:,1) - 0.5*(rgb(:,:,2)+rgb(:,:,3));
% use xc below to just look at selected region
bw1 = and(xd>y(1),xd<y(2));
sz = size(bw1);
%fprintf('%g included\n',sum(sum(bw1))/(sz(1)*sz(2)));
imshow(~bw1);

chroma x range: -0.231373 0.196078

hist = imhist((yc+1)/2);
% y = func1(hist);
sy = sort(yc(:));
y(1) = sy(10);
y(2) = sy(end-9);
fprintf('chroma y range: %g %g\n',y);
yd = sqrt(3)/2 * ( rgb(:,:,2) - rgb(:,:,3));
% use yc below to just look at selected region
bw2 = and(yd>y(1),yd<y(2));
sz = size(bw2);
% fprintf('%g included\n',sum(sum(bw2))/(sz(1)*sz(2)));
imshow(~bw2);

chroma y range: 0.0509427 0.516219

imshow(~(bw1&bw2));

bw = ~(bw1&bw2);
imshow(cat(3,rgb(:,:,1).*bw,rgb(:,:,2).*bw,rgb(:,:,3).*bw));