basics

imread
imwrite
imhist
imfinfo % fileinfo
imgetfile
imshow(I, [low high]) %show all values =< low and >= high


%convert matrix values to intensity values between 0 and 1
I = mat2gray(A,[AMIN AMAX])

im2bw
im2double

im2uint8(I) %Convert image to 8-bit unsigned integers

% array operation
v = round(rand(1,5)*100)


>> v = round(rand(1,10)*100)
v =
    14    42    92    79    96    66     4    85    93    68

>> v(3:3)
ans =
    92


>> v(3:4)
ans =
    92    79

>> v(8:end)
ans =
    85    93    68


% start start at position 1, and take every 5th element till end
>> v(1:5:end)
ans =
    14    66

%do the same reverse ...
>> v(end:-5:1)
ans =
    68    96
    
% creates n values between a and b
% linspace(a,b,n)
>> linspace(0,5,3)
ans =
         0    2.5000    5.0000

%generators
rand %uniformly distributed
randn % normally distributed (gaussian 0 and variance 1)
ones
zeros
true
false
magic

%image operations
imadd
imsubtract
immultiply
imdivide
imabsdiff
imcomplement
imlincomb % linear combination of two or more images

%queries
all() % all values are > 0
any % any value is > 0
xor % both operand are logically different

down_scaling

I = imread('rose.tif');
%a=round(rand(4,4)*100)
k=uint8( down_Scaling(I, 0.5));
imshow(k)
figure
imshow(I)

function z = down_Scaling(I, factor)
    I_new = zeros(size(I)*factor);
    [width_orig,height_orig] = size(I);
    
     rIndex=1;
     for r=1:inv(factor):height_orig
        cIndex = 1;
        for c=1:inv(factor):width_orig
            I_new(rIndex,cIndex) = I(r,c);
            cIndex = cIndex + 1;
        end
        
         rIndex = rIndex + 1;
     end
    
    z = I_new;
end