x=imread（‘1.bmp‘）;
subplot（131）;
imshow（x）;
title（‘原圖‘）;
[mn]=size（x）;
M=128;

??????%???????投影????????%
??????
proj1=zeros（128128）;?????%?????定義一個128X128維的零矩陣?????%???
for?N=1:128???????????????%?????設置128個投影角度?????????????%
????t=N*pi/128;???????????%?????定義每個投影角度大小??????????%
????for?i=1:64
????????for?j=1:64
????????????y1=（i-n/2）*cos（t）+（j-m/2）*sin（t）;??%???radon?變換????%
????????????z1=floor（y1）;???????????????????????%???取整??????????%
????????????proj1（Nz1+64）=radon（Nz1+64）+double（x（ij））*（z1+1-y1）;???%?????插值?????%
????????????proj1（Nz1+1+64）=radon（Nz1+1+64）+double（x（ij））*（y1-z1）;
????????end
????end
end
subplot（132）;
imshow（proj1/10000）;
title（‘投影圖‘）;

??????????????%?????反投影???????%
????????
proj2=fftshift（fft2（proj1））;
proj3=zeros（1M）;
proj3=double（proj3）;

?????????????%?????構建Ramp濾波器???????%
for?i=1:M????????????????????????
????proj3（i）=abs（i-M/2.0）/（M/2.0）;
end
proj3=proj3（ones（1281）:）;
proj2=proj2.*proj3;???

?????????????%?????構建高斯低通濾波器???%
d=zeros（MM）;
for?i=1:M
????for?j=1:M
????????d（ij）=（（i-（2*M+1）/4）^2+（j-（2*M+1）/4）^2）^.5;
????end
end??
???????????%???????指定高斯濾波器截止頻率?Do??%
Do=60;??????????
Gauss_L=exp（-（（d.^2）./（2*Do^2）））;
proj2=proj2.*Gauss_L;???????%????Ramp濾波器與高斯低通濾波器相乘????%
proj4=abs（ifft2（proj2））;
A=max（max（proj4））-min（min（proj4））;
proj4=（proj4-min（min（proj4）））./A.*255;?????%???濾波后投影proj4????%

proj5=zeros（128128）;
for?i=1:128
????for?j=1:128
????????x=double（j）-（M+1）/2.0;
????????y=（M+1）/2.0-double（i）;
????????t=pi/128.0;
????????for?n=1:128
????????????s1=x*cos（（n-1）*t）+y*sin（（n-1）*t）+M/2.0;
????????????if?s1<=M&s1>=1
???????????????proj5（ij）=proj5（ij）+（proj4（nfloor（s1））+（s1-floor（s1））*（proj4（nfloor（s1）+1）））;
????????????end
????????end
????end
end
B=max（max（proj5））-min（min（proj5））;????%灰度拉伸
subplot（133）;
proj5=（proj5-min（min（proj5）））.*（255/B）;
imshow（uint8（proj5））;
title（‘濾波反投影圖D。=60.bmp‘）;

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????5176??2009-05-14?10:45??實驗五\1.bmp

?????文件???????2040??2009-06-07?20:38??實驗五\project.m

?????文件?????123392??2009-06-08?21:51??實驗五\實驗報告.doc

?????文件????????160??2009-06-08?21:48??實驗五\實驗說明.txt

?????目錄??????????0??2009-06-10?12:43??實驗五

-----------?---------??----------?-----??----

???????????????130768????????????????????5