Can any one explain the following code which implements CBIR..??

function CBIR_Query(q_imgid, dist_id, lamda)

imgdir = 'D:\ENTRY LEVEL\M.Tech Seminar & Project\Project\DB\1000 images\';

fetdir = 'D:\ENTRY LEVEL\M.Tech Seminar & Project\Project\DB\1000 images\';

imgno = 1:1000;

imgsuffix = '.jpg';

q_imgid=input('Enter the Query Image (1~1000):');

dist_id = [3 3];

lamda = 0.7;

t1=tic;

q_feature = load([fetdir,num2str(q_imgid),'.mat']);

q_feature = q_feature.feature;

dist = zeros(2, length(imgno));

for i=imgno

load([fetdir,num2str(i),'.mat']);

if dist_id(1) == 1

dist(1,i) = dist(1,i) +

CBIR_L2dist(q_feature.colorhist, feature.colorhist);

elseif dist_id(1) == 2

dist(1,i) = dist(1,i) +

CBIR_cosinedist(q_feature.colorhist,feature.colorhist);

elseif dist_id(1) == 3

dist(1,i) = dist(1,i) +

CBIR_histintersection(q_feature.colorhist,feature.colorhist);

end

if dist_id(2) == 1

dist(2,i) = dist(2,i) +

CBIR_L2dist(q_feature.edgedirection,feature.edgedirection);

elseif dist_id(2) == 2

dist(2,i) = dist(2,i) +

CBIR_cosinedist(q_feature.edgedirection, feature.edgedirection);

elseif dist_id(2) == 3

dist(2,i) = dist(2,i) +

CBIR_histintersection(q_feature.edgedirection,feature.edgedirection);

end

end

w = [lamda 1-lamda];

c_dist = w*dist;

[score(1,:), score(2,:)] = sort(c_dist);

N = 20; C = 4; R = 5; ct=0;

figure

for i = 1 : N

ct=ct+1;

img = imread([imgdir,num2str(score(2,i)),imgsuffix]);

subplot(C, R, i);

imshow(img);

end

precision=ct/20;

precision

recall=ct/100;

recall

fprintf('Time calculated for Color and Shape Feature only \n');

toc(t1)

function dist = CBIR_histintersection(x1, x2)

dist = sum(min([x1(:)'; x2(:)']));

denom = min([sum(x1(:)),sum(x2(:))])+1e-8;

dist = dist/denom;

dist = 1-dist;

function CBIR_featurecalc()

imgdir = 'D:\ENTRY LEVEL\M.Tech Seminar & Project\Project\DB\1000 images\';

fetdir = 'D:\ENTRY LEVEL\M.Tech Seminar & Project\Project\DB\1000 images\';

imgno = 1:1000;

imgsuffix = '.jpg';

for i=imgno

imgrgb=imread([imgdir,num2str(i),imgsuffix]);

feature.colorhist = CBIR_colorhist(imgrgb);

feature.edgehist = CBIR_edgehist(imgrgb);

feature.edgedirection = CBIR_edgedirection(imgrgb);

save([fetdir,num2str(i),'.mat'], 'feature');

end

function edgehist = CBIR_edgehist(rgb)

imgsize = size(lum);

i0=round(0.05*imgsize(1)); i1=round(0.95*imgsize(1));

j0=round(0.05*imgsize(2)); j1=round(0.95*imgsize(2));

lum = lum(i0:i1, j0:j1);

imgsize = size(lum);

edgemask(:,:,1) = [1 -1; 1 -1];

edgemask(:,:,4) = [1 1; -1 -1];

edgemask(:,:,2) = [sqrt(2) 0; 0 -sqrt(2)];

edgemask(:,:,3) = [0 sqrt(2); -sqrt(2) 0];

edgemask(:,:,5) = [2 -2; -2 2];

TH = 100*ones(1,5);

edgedir = [{'0^o'} {'45^o'} {'-45^o'} {'90^o'} {'iso'}];

for i = 1:5

gradient = filter2(edgemask(:,:,i), lum, 'same');

edgehist(i) = sum(abs(gradient(:))>TH(i));

end

edgehist = edgehist/prod(imgsize);

function edgehist = CBIR_edgedirection(rgb)

imgsize = size(lum);

i0=round(0.05*imgsize(1)); i1=round(0.95*imgsize(1));

j0=round(0.05*imgsize(2)); j1=round(0.95*imgsize(2));

lum = lum(i0:i1, j0:j1);

imgsize = size(lum);

sobel_y = [1 0 -1; 2 0 -2; 1 0 -1];

sobel_x = [1 2 1; 0 0 0; -1 -2 -1];

g_x = filter2(sobel_x, lum, 'same');

g_x = g_x + (g_x==0)*1e-6;

g_y = filter2(sobel_y, lum, 'same');

tg = g_y./g_x;

edgemap = edge(lum, 'sobel');

TH = [ tan(pi/8), tan(pi*3/8), tan(-pi/8), Inf; ... tan(-pi/8), tan(pi/8), tan(-pi*3/8), tan(pi*3/8)];

edgedir = [0 45 -45 90];

for i = 1:4

if i~=4

directmap = (tg<TH(1,i) & tg>=TH(2,i));

else

directmap = ((abs(tg)<TH(1,i)) & (abs(tg)>=TH(2,i)));

end

edgehist(i) = sum(sum(directmap & edgemap));

end

edgehist = edgehist/prod(imgsize);

function colorhist = CBIR_colorhist(rgb)

H_BITS = 4;

S_BITS = 2;

V_BITS = 2;

hsv = uint8(255*rgb2hsv(rgb));

imgsize = size(hsv);

i0=round(0.05*imgsize(1)); i1=round(0.95*imgsize(1));

j0=round(0.05*imgsize(2)); j1=round(0.95*imgsize(2));

hsv = hsv(i0:i1, j0:j1, :);

for i = 1 : 2^H_BITS

for j = 1 : 2^S_BITS

for k = 1 : 2^V_BITS

colorhist(i,j,k) = sum(sum( ...

bitshift(hsv(:,:,1),-(8-H_BITS))==i-1 &...

bitshift(hsv(:,:,2),-(8-S_BITS))==j-1 &...

bitshift(hsv(:,:,3),-(8-V_BITS))==k-1 ));

end

end

end

colorhist = reshape(colorhist, 1, 2^(H_BITS+S_BITS+V_BITS));

colorhist = colorhist/sum(colorhist);