how can i solve median filter 5x5 on image on lena?

hello,i have a project of image processing,it is a median filter 5x5 ,i have to use it on standart pictures like lena etc, without using toolbox coding as medfilter,etc,i have to write an algorithm for that,i am new on matlab and still have a problem on Subscripted assignment dimension mismatch. i didnt remove it , please contact with me, because i have a little time to submit it.

for i=(a+1)/2:height-((a-1)/2)
for  j=(a+1)/2: height-((a-1)/2)
templena =lena(i-(a-1)/2:i+(a-1)/2,j-(a-1)/2:j+(a-1)/2);
x=median(templena);
lenaoutput(i,j)=x;
end
end

i will appreciate you , if i can solve it. thank you again

[Geoff Hayes]

What is a? What is height defined to be, and should there be a width as well? Ideally, the code should process each pixel and consider the 5x5 neighbourhood around it taking care when the neighbourhood runs outside of the image.

Answer 1

[Image Analyst]

You need to have the outer loops scan over rows and columns, then extract a subimage and call median (if you're allowed to use that function).

windowHeight = 5;
windowWidth= 5;
[rows, columns, numberOfColorChannels] = size(grayImage);
for c = ceil(windowWidth/2) : columns - ceil(windowWidth/2)
  for r = ceil(windowHeight/2) : rows - ceil(windowHeight/2)
      subimage = grayImage(..............
  end
end

Try to finish it.

[fatma]

my code is like this. >> uiopen('C:\Users\LG\Desktop\lena.pgm',1)

lena1=imread('C:\Users\LG\Desktop\lena.pgm');

>> lena=imnoise(lena1,'salt & pepper',0.01);

>> imshow(lena)

lena=double(lena);

>> height=size(lena,1);

>> width=size(lena,2);

>> lenaoutput=zeros(size(lena));

>> for i=3 :height-2

for j=3 :height-2

templena=lena(i-1: i+3,j-1:j+3);

w=[lena(i-1,j-1) lena(i,j-1) lena(i+1,j-1) lena(i+2,j-1) lena(i+3,j-1) lena(i-1,j) lena(i,j) lena(i+1,j) lena(i+2,j) lena(i+3,j) lena(i-1,j+1) lena(i,j+1) lena(i+1,j+1) lena(i+2,j+1) lena(i+3,j+1) lena(i-1,j+2) lena(i,j+2) lena(i+1,j+2) lena(i+2,j+2) lena(i+3,j+2) lena(i-1,j+3) lena(i,j+3) lena(i+1,j+3) lena(i+2,j+3) lena(i+3,j+3)]

m=median(w);

pixvalue=m;

lenaoutput(i,j)=pixvalue;

lenaoutput(1,j)=lenaoutput(2,j);

for i=1 :2

for j=1 :256

lenaoutput(i,j)=lenaoutput(3,j);

end;

end;

for i=1 : 256

for j=1 :2

lenaoutput(i,j)=lenaoutput(i,3);

end

end;

for i=255: 256

for j=1:256

lenaoutput(i,j)=lenaoutput(254,j);

end

end;

for i=1 :256

for j=255 :256

lenaoutput(i,j)=lenaoutput(i,254);

end

end;

lenaoutput=uint8(lenaoutput);

imshow(lenaoutput)

 but i couldnt see the lenaoutput image , there is no result.please  help me to solve it because i dont know  where i did a mistake.i have little time to submit it,and still couldnt see the results.

[Image Analyst]

Learn how to write a script instead of doing everything on the command line. Also learn to format your code by watching this: http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Also if I take time to give you good advice, it might be good if you followed it, because there may be reasons why I didn't try to fix your existing code (like it's so bad that it's not worth fixing).