Why perform (figures) all black?

 clear all
 [filename pathname] = uigetfile({'*.tif'},'Select A Video File');
 I = imread([pathname,filename]);

 I=double(I);
 [hue,s,v]=rgb2hsv(I);
 cb =  0.148 * I(:,:,1) - 0.291 * I(:,:,2) + 0.439 * I(:,:,3) + 128;
 cr =  0.439 * I(:,:,1) - 0.368 * I(:,:,2) - 0.071 * I(:,:,3) + 128;
 [w h]=size(I(:,:,1));
 for i=1:w
     for j=1:h            
         if  140<=cr(i,j) && cr(i,j)<=165 && 140<=cb(i,j) && cb(i,j)<=90 && 0.01<=hue(i,j) &&  hue(i,j)<=0.1     
             segment(i,j)=0;            
         else       
             segment(i,j)=0;    
         end    
     end
 end

 im(:,:,1)=I(:,:,1).*segment;   
 im(:,:,2)=I(:,:,2).*segment; 
 im(:,:,3)=I(:,:,3).*segment;  
 figure (1),imshow(uint8(im));

 im2= rgb2gray (im);
 figure (2),imshow(im2);

 umb = graythresh(im2);
 bw =    im2bw (im2,umb);
 edge=edge(bw,'canny',[0.15, 0.3]);
 figure (3), imshow(edge);

 L2 = imfill(edge,'holes');
 figure (4), imshow(L2);

 [L Ne]=bwlabel (bw);
 propied  = regionprops(L);

 hold on;

 for n=1:size(propied,1)
    rectangle('Position', propied(n).BoundingBox,'EdgeColor','g','LineWidth',2)
 end
  pause(3)
  s = find([propied.Area]<300);
   for n = 1: size (s,2)
     rectangle('Position', propied(s(n)).BoundingBox,'EdgeColor','r','LineWidth',2)
   end
  pause(2)

for n = 1: size(s,2)
   d=round(propied(s(n)).BoundingBox); 
   bw(d(2):d(2)+d(4), d(1):d(1)+d(3))= 0; 
end
figure (5), imshow(bw);

s2 = find([propied.Area]>1000);
I2=imcrop(bw,propied(s2(1)).BoundingBox);
figure (6),imshow(I2)   ;

Answer 1

[Image Analyst]

There is either nothing there, or they're double. Try adding [] to imshow():

imshow(L2, []);