Please explain this QR code program to me.

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S. M
S. M 2022-1-3
编辑： Walter Roberson 2022-1-4
I wanna someone explain to me what every functions do ,special functions QRkey and im2freqs ?total code will extract Qr code from image
function [ hit ] = QRkey( img,L,RP ) hit=[]; [row ~] = size(img); for i = 1:row freq = im2freqs(img(i,:)); [num ~] = size(freq); for j = 3:num-3 Error = 0.5; if abs((freq(j,2)/3)-freq(j-2,2)) > ceil((freq(j,2)/3)*Error)+1 ... abs((freq(j,2)/3)-freq(j-1,2)) > ceil((freq(j,2)/3)*Error)+1 ... abs((freq(j,2)/3)-freq(j+1,2)) > ceil((freq(j,2)/3)*Error)+1 ... abs((freq(j,2)/3)-freq(j+2,2)) > ceil((freq(j,2)/3)*Error)+1 ... freq(j,3)==0 L(i,freq(j,1))==0 L(i,freq(j+2,1))==0 L(i,freq(j-2,1))==0 continue; end %x = freq(j,1) , y = i Box = RP( L(i,freq(j,1)) ).BoundingBox; Cdif = uint32(sum(abs(RP(L(i,freq(j+2,1))).Centroid - RP(L(i,freq(j,1))).Centroid))); Ar = RP( L(i,freq(j,1)) ).Area;
if Cdif <= 5 && ...
L(i,freq(j-2,1))==L(i,freq(j+2,1)) && L(i,freq(j-2,1))~=L(i,freq(j,1))
hit = [hit; L(i,freq(j,1))];
j = j+2;
end
end
end
end
function [ freq ] = im2freqs( img)
col = numel(img);
freq = [];
co = [1 1 img(1)]; % [center counter color]
for j = 2:col
if co(3) ~= img(j)
co(1) = uint32(co(1))+ uint32(co(2))/2;
freq = [freq ; co];
co = [j 1 img(j)];
else
co(2) = co(2) + 1;
end
end
co(1) = uint32(co(1))+ uint32(co(2))/2;
freq = [freq;co];
end
function QR = CropQR (img, points) %u = [points(2,:)-points(4,:) 0]; %v = [1 0 0]; %c = cross(u,v); %angle = sign(c(3))*180/pi*atan2(norm(c),dot(u,v)); %angle = -(mod(angle +360,360)-135); angle = atand((points(2,2)-points(4,2))/(points(2,1)-points(4,1))); angle = angle - 45; if points(4,1) < points(2,1) angle = angle + 180; end
[h ,w ,~] = size(img);
QR = imrotate(img, angle);
[rh ,rw ,~] = size(QR);
T=[w/2 h/2];
RT=[rw/2 rh/2];
R=[cosd(angle) -sind(angle); sind(angle) cosd(angle)];
T = [T;T;T;T];
RT = [RT;RT;RT;RT];
rotpoints=(points-T)*R+RT ;
rotpoints=uint32(rotpoints);
xymax = max(rotpoints);
xymin = min(rotpoints);
QR = QR(xymin(2):xymax(2), xymin(1):xymax(1), :);
end
function [ ] = QRextraction( Rimg ) Rimg = imread('6.1.bmp'); img = rgb2gray(Rimg);
%sharppining the image
%enhancment image % and convert to binary image (black and white)
img = imsharpen(img,'Radius',10,'Amount',1);
img = ~im2bw(img,0.5);
[L num] = bwlabel(img)
%now we need properties for each 8 component
RP = regionprops(L,'all');
hit = QRkey(img,L,RP);
hit = [unique(hit) histc(hit,unique(hit))]
figure,imshow(L );
flag = zeros((numel(hit)/2));
for i = 1:(numel(hit)/2)-1
if flag(i)==1
continue;
end
ci = RP(hit(i,1)).Centroid;
j = i+1;
if flag(j)==1
continue;
end
cj = RP(hit(j,1)).Centroid;
for k = 1:(numel(hit)/2)
if i == k || j == k || flag(k)==1
continue;
end
ck = RP(hit(k,1)).Centroid;
%start
a = pdist([ci ; cj],'euclidean');
b = pdist([ci ; ck],'euclidean');
c = pdist([cj ; ck],'euclidean');
diff = cj - ci;
if c<a || c<b
continue;
end
d = ck+diff;
zz = abs((a*a + b*b)-(c*c))/(c*c)
center = ((cj+ci+ck+d)/4);
if zz < 0.1
x = [cj(1);ci(1);ck(1);d(1)];
y = [cj(2);ci(2);ck(2);d(2)];
x = x+(x-center(1))*0.5;
y = y+(y-center(2))*0.5;
flag(i)=1;flag(j)=1;flag(k)=1;
final_image=CropQR( Rimg , [x y]);
figure,imshow(final_image);
break;
end
end
end
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回答（1 个）

yanqi liu
yanqi liu 2022-1-4
编辑：Walter Roberson 2022-1-4
yes，sir，i think the key is to judge the square corner，such as
now，we can find the rule
a = pdist([ci; cj],'euclidean');
b = pdist([ci; ck],'euclidean');
c = pdist([cj; ck],'euclidean');
zz = abs((a*a + b*b)-(c*c))/(c*c);
when zz < 0.1 ，the area is QR area，such as

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