Converting RGB image to Binary Image without using im2bw function

         In the first example, image is filled with primary colors (RGB). So I am finding the sum of the values in the pixel position. If the sum is greater than zero then the value will be 1(white) otherwise zero (black).

       In the second example, the following steps are needed to convert a RGB image to binary image.

1. Convert the RGB image into grayscale image.
2. Find the threshold value. If the value at the pixel position is greater than the threshold value then the value will be 1(white) else zero (black).
   
   

   
   function mybinary
   
   global GIm T1;
   
   A=imread('shapes.bmp');
   
   figure,imshow(A);
   
   title('Original image');
   
   B=zeros(size(A,1),size(A,2));
   
   for l=1:size(A,1)
   
       for m=1:size(A,2)
   
           if(sum(A(l,m,:))>0)
   
               B(l,m)=1;
   
           end
   
       end
   
   end
   
   B=logical(B);
   
   figure,imshow(B);
   
   
   

   
   
   
   
   
   
   

   
   Im=imread('gantrycrane.png');
   
   
   
   figure,imshow(Im);
   
   title('Original Image');
   
   %0.2989 * R + 0.5870 * G + 0.1140 * B
   
   GIm=uint8(zeros(size(Im,1),size(Im,2)));
   
   for m=1:size(Im,1)
   
       for n=1:size(Im,2)
   
           GIm(m,n)=0.2989*Im(m,n,1)+0.5870*Im(m,n,2)+0.1140*Im(m,n,3);
   
       end
   
   end
   
   
   

   we can perform the grayscale conversion without using the for loop:
   
   

   %GIm=0.2989*Im(:,:,1)+0.5870*Im(:,:,2)+0.1140*Im(:,:,3);

   
   
   
   

   
   
   ssz = get(0,'ScreenSize');
   
   T.fg=figure('Visible','on','Name','IMAGE THRESHOLDING','NumberTitle','off','Position', ssz);
   
   T.holder=axes('units','pixels','Position',[ssz(3)/35 ssz(4)/4 ssz(3)-(ssz(3)/3) ssz(4)-(ssz(4)/3)]);
   
   
   
   imshow(GIm);
   
   set(T.holder,'xtick',[],'ytick',[])
   
   
   
   
   
   T.slid=uicontrol('Style','Slider','Visible','on','Value',1,'Max',255,'Min',0,'Sliderstep',[1 1],'Position',[ssz(3)/35 ssz(4)/5 ssz(3)-(ssz(3)/3) 20],'Callback', @tresher);
   
   T.ent=uicontrol('Style','pushbutton','Visible','on','String','THRESHOLD VALUE','Position',[ssz(3)-(ssz(3)/4) ssz(4)-(ssz(4)/8) 105 30]);
   
   T.ed=uicontrol('Style','edit','Visible','on','String','0','Value',1,'Position',[ssz(3)-(ssz(3)/4) ssz(4)-(ssz(4)/6) 90 20]);
   
   
   
         function tresher(object,~)
   
           val=get(object,'value');
   
           in=GIm;
   
           T1=Imthreshold1(in,val);
   
           T.view1=imshow(T1);
   
           set(T.holder,'xtick',[],'ytick',[])
   
          
   
           set(T.ed,'String',val);
   
         end
   
   
   
                                                                                
   
                                                                                
   
                                                                                
   
                                                                                
   
                                                                                
   
                                                                                
   
   
   
   
     function Im=Imthreshold1(Image,Tvalue)
   
   sz=size(Image);
   
   
   mybin=zeros(size(Image));
   
   
   
   
   
   
   for i=1:sz(1)
   
       for j=1:sz(2)
   
           if(Image(i,j)>Tvalue)
   
               mybin(i,j)=1;
   
              
   
           end
   
       end
   
   end
   
   

   
   
   
   Instead of this for loop, the equivalent one line code is:
   
   

   %mybin(find(Image>Tvalue))=1;

   
   

   Explanation:

   The output of find(Image>Tvalue) will be the values that are greater than Tvalue.

   
   

   
   

   
   

   For instance,

   consider a matrix,

   
   

   >> A=[1,2,3,4;2,4,6,8;3,6,9,12];

   >> A

   
   

   A =

   
   

        1     2     3     4

        2     4     6     8

        3     6     9    12

   
   

   >> find(mod(A,2)==0)

   
   

   ans =

   
   

        2

        4

        5

        6

        8

       10

       11

       12

   
   

   
   

   
   
   
   

   
   
   Im=logical(mybin);
   
   end
   
   
   
   end