基于双边滤波的图像处理，为什么会输出两个黑框？以下代码

clear all;
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clc;

img=imread('t_2.jpg');+ o3 L9 H1 b1 k- V3 ]
img=mat2gray(img);
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%imshow(img);

r=10; %模板半径
/ o3 N  t7 l: w; F% C7 m. T3 N# Kimgn=zeros(m+2*r+1,n+2*r+1);
1 [2 S2 L+ T# [. v$ T; Gimg=imgn(r+1:m+r,r+1:n+r);+ m( C4 V: S& C3 F9 h( J
imgn(1:r,r+1:n+r)=img(1:r,1:n); %扩展上边界
. m6 J; H' g* g. Y! f( Zimgn(1:m+r,n+r+1:n+2*r+1)=imgn(1:m+r,n:n+r); %扩展右边界* t- D; E" ^2 J" J; W& I
imgn(m+r+1:m+2*r+1,r+1:n+2*r+1)=imgn(m:m+r,r+1:n+2*r+1); %扩展下边界- G- @% w, M! c+ F# z6 u
imgn(1:m+2*r+1,1:r)=imgn(1:m+2*r+1,r+1:2*r); %扩展左边界

sigma_d=2;
! l: `9 g0 {% {0 m6 Wsigma_r=0.1;
+ q9 ]& @8 I2 _: S0 ], y[x,y] = meshgrid(-r:r,-r:r);
/ Y/ b; h* q( Hw1=exp(-(x.^2+y.^2)/(2*sigma_d^2)); %以距离作为自变量高斯滤波器

h=waitbar(0,'wait...');
- G, z: u. d) k% m; u2 B. Mfor i=r+1:m+r. V" H- w) n5 z, J! v+ ?) b
for j=r+1:n+r
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w2=exp(-(imgn(i-r:i+r,j-r:j+r)-imgn(i,j)).^2/(2*sigma_r^2)); %以周围和当前像素灰度差值作为自变量的高斯滤波器4 P/ ^4 m1 x$ P9 }! X
w=w1.*w2;

end
0 W) C8 ^& V" ^8 zclose(h)

figure;
* `$ o5 k% ?; T% a$ qimshow(mat2gray(imgn(r+1:m+r,r+1:n+r)));

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