function?result=canny（IszT1T2）
%?perform?canny?edge?detector.?I?is?the?input?image?sz?indicates?the?size
%?of?gaussian?T1?is?the?lower?threshold?and?T2?is?the?upper?threshold.

%?smooth?the?image?with?a?gaussian?filter
h=fspecial（‘gaussian‘szsz/6）;
I=imfilter（Ih‘replicate‘）;
I=double（I）;

%?choose?priwitt?to?compute?the?gradient?magnitude?image?g（xy）
GX=[-1?-1?-1;?0?0?0;?1?1?1]??;%?Gx
GY=[-1?0?1;-1?0?1;?-1?0?1];???%?Gy
I1=imfilter（IGX‘replicate‘）;
I2=imfilter（IGY‘replicate‘）;
g=sqrt（I1.^2+I2.^2）;


[xy]=size（I）;?%?get?the?size?of?I.
%?compute?the?edge?direction?image?theta（xy）
theta=zeros（xy）;
for?i=1:x
????for?j=1:y
????????if（I1（ij）==0?&&?I2（ij）==0）?????%?if?both?Gx?and?Gy?are?equal?to?0?set?the?direction?to?be?0
????????????theta（ij）=0;
????????else
????????????theta（ij）=atan（I2（ij）./I1（ij））*180/3.1415926;?%?get?the?direction?in?degrees.
????????end
????????%?set?the?direction‘s?range?to?be?[0360]
???????if（I1（ij）>=0&&I2（ij）<0）
???????????theta（ij）=theta（ij）+360;
???????elseif（I1（ij）<0&&I2（ij）>=0）
???????????theta（ij）=theta（ij）+180;
???????elseif（I1（ij）<0&&I2（ij）<0）
???????????theta（ij）=theta（ij）+180;
???????end
???????
????end
end

%?quantize?the?angle?to?the?nearest?angle:{04590135180225270315360}
angle=（0:8）*45;
for?i=1:x
????for?j=1:y
????????for?k=1:9
????????????if（abs（theta（ij）-angle（k））<=45/2）
????????????????theta（ij）=angle（k）;
????????????end
????????end
????end
end

%?call?localmax?function?to?perform?the?nonmaximal?supression
G=localmax（gtheta）;
G=uint8（G）;

G（find（G>T2*max（G（:））））=255;?%?change?the?pixels?above?upper?threshold?to?be?edges.
G