MATLAB: How to change specific RGB value to another RGB value in a PNG uint8 image

change rgb value

%I have the following code:
RGB = imread('image.png');
[r c z] = size(RGB);
for i=1:r
for j=1:c
if (RGB(i,j,1)==50 && RGB(i,j,2)==205 && RGB(i,j,3)==50) 
RGB(i,j,1)=255; RGB(i,j,2)=255; RGB(i,j,3)=255;
elseif (RGB(i,j,1)==255 && RGB(i,j,2)==228 && RGB(i,j,3)==181)
RGB(i,j,1)=255; RGB(i,j,2)=255; RGB(i,j,3)=255;
elseif (RGB(i,j,1)==0 && RGB(i,j,2)==0 && RGB(i,j,3)==0) %MATLAB won't run this part
RGB(i,j,1)==255 && RGB(i,j,2)==255 && RGB(i,j,3)==255;
elseif (RGB(i,j,1)==250 && RGB(i,j,2)==250 && RGB(i,j,3)==250) %MATLAB also won't run this part
RGB(i,j,1)==255 && RGB(i,j,2)==255 && RGB(i,j,3)==255;
  else
      RGB(i,j,1)=0; RGB(i,j,2)=0; RGB(i,j,3)=0;
        end 
    end
end
%So that's my code
the original image is here: https://dl.dropboxusercontent.com/u/9183365/image.png
My problem now is why MATLAB does not change the RGB values as indicated in the code comments? Also, is there a way to use operators to simplify the code instead of using so much elseifs? I shall be using this for one of my clustering algorithms. Thank you so much in advance for any help.

Best Answer

You have
elseif (RGB(i,j,1)==0 && RGB(i,j,2)==0 && RGB(i,j,3)==0) %MATLAB won't run this part
RGB(i,j,1)==255 && RGB(i,j,2)==255 && RGB(i,j,3)==255;
You want to do assignments not tests, same kind of structure as you had used already where you had
RGB(i,j,1)=255; RGB(i,j,2)=255; RGB(i,j,3)=255;
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