Ok, I find it!
RGB=imread(I);
%%Convert to gray scale
Gray=rgb2gray(RGB);
%%Convert to binary image
threshold = graythresh(Gray);
imagen =~im2bw(Gray,threshold);
%%Remove all object containing fewer than 30 pixels
imagen = bwareaopen(imagen,30);
%%Label connected components
[L Ne]=bwlabel(imagen);
%%Measure properties of image regions
propied=regionprops(L,'BoundingBox','Area');
% %%Objects extraction
for n=1:Ne
if(propied(n).Area>1000)
[r,c] = find(L==n);
switch (type)
case 'RGB'
%%get the image of the object
s_I=size(RGB);
s = size(r);
n1(:,:,1) = zeros(s_I(1),s_I(2));
n1(:,:,2) = zeros(s_I(1),s_I(2));
n1(:,:,3) = zeros(s_I(1),s_I(2));
n1 (:,:,1) =255;
n1 (:,:,2) = 255;
n1 (:,:,3) = 255;
for i=1:s
n1(r(i),c(i),1)=RGB(r(i),c(i),1);
n1(r(i),c(i),2)=RGB(r(i),c(i),2);
n1(r(i),c(i),3)=RGB(r(i),c(i),3);
end;
n1 = uint8(n1);
% get the croped object from the image
R = n1(min(r):max(r),min(c):max(c),1);
G = n1(min(r):max(r),min(c):max(c),2);
B = n1(min(r):max(r),min(c):max(c),3);
n2 = cat(3,R,G,B);
n2 = uint8(n2);
that is it! Hope it will help someone.
