i have following image in double(i.e range is 0-1) & i want to convert it to 1's and -1's form,just convert 0 to -1.i tried foll code but its not working.please help. :(

%%just try the foll code:

[d1,d2,d3]=size(img);

for i=1:d1
   for j=1:d2
     if img(i,j)==0
        img(i,j)=-1
     end
  end
end

%display it and see impixelinfo;
%0 should get converted to -1
%and 1 as it is.

take attached sample img.

Answer 1

[David Sanchez]

I=rgb2gray(rp7);
I2=im2bw(I);
I3 = double(I2);
I3(I2==0) = -1;

[David Sanchez]

rp7 is your image

[Walter Roberson]

Or once I3 has been created,

I3 = I3 * 2 - 1;

without using the logical indexing.