Reducing Size of image Algorithm in Matlab

%% Algorithm for minimizing the size of the object
clc
clear all
a=imread('3.png');
imshow(a)
[r,c]=size(a);
i=1;j=1;
c=c/3;
b=zeros(floor(r/2),floor(c/2));
for x=1:2:r
for y=1:2:c
b(i,j)=a(x,y);
j=j+1;
end
i=i+1;
j=1;

end
figure
imshow(b/255),colormap(colorcube)
figure
imagesc(b/255),colormap(gray)
impixelinfo