Arithmetic Coding in Digital Image Processing with example&its Implementation in MATLAB||Compression

Video lecture series on Digital Image Processing, Lecture: 40,
Arithmetic coding in Digital Image Processing with example and its Implementation in MATLAB
Link to download ppts/lecture notes:
https://drive.google.com/drive/folder...
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MATLAB codes...
% % %Program for Arithmetic
close all;
clear all;
clc;
str = 'dafda';
fprintf('The entered string is : %s\n', str);
len = length(str);
fprintf('The length of the string is : %d\n', len);

% % % get unique characters from the string
u = unique(str)
% disp('the unique symbols/characters are');
% disp(u);
fprintf('The unique characters are : %s\n', u);
len_unique = length(u);
fprintf('The length of unique character string is : %d\n', len_unique);
% % % General lookup table
% % % get zeros of length of unique characters
z = zeros(1, len_unique);
p = zeros(1, len_unique);

for i = 1 : len_unique

% % % in 'z' variable we find the occurrence of each characters from 'str'
z(i) = length(findstr(str, u(i)));

% % % in 'p' variable we will get probability of those occurrences
p(i) = z(i) / len;
end
display(z);
display(p);

% % % in 'cpr' variable we will get the cumulative
cpr = cumsum(p);
% % % in 'newcpr' 'cpr' from '0' till last value of 'p'
newcpr = [0 cpr];

display(cpr);
display(newcpr);

% % % make table upto size of 'len_unique'
for i = 1 : len_unique

% % % in first column we are placing 'newcpr' values
table(i, 1) = newcpr(i);

% % % in second column we are placing 'cpr' values
table(i, 2) = cpr(i);
end

% % % Displaying the lookup table
display('The lookup table is : ')
display(table);

% % % Encoder Table

LL = 0;
HL = 1;
for i = 1 : len
for j = 1 : len_unique

% % % if the value from 'str' matches with 'u' then
if str(i) == u(j);
pos = j;
j = j + 1;

% % % displaying position of symbol in unique string
display(pos);

% % % getting the tag value of the matched character
diff_range = HL - LL
HL = LL + (diff_range .* table(pos, 2))
LL = LL + (diff_range .* table(pos, 1))
i = i + 1;
break
end
end
end
% % % displaying tag value
tag = LL;
display(tag);
%%% DECODING %%%
str = '';
% str = [];
for i = 1 : len
for j = 1 : len_unique
% % % If tag value falls between a certain range in lookup table then
if tag (greater than or)= table(j, 1) && tag (less than) table(j, 2)
pos = j;
tag = (tag - table(pos, 1)) / p(j);

% % % Getting the matched tag value character
decoded_str = u(pos);

% % % String concatenating 'decoded_str' into 'str'
str = horzcat(str, decoded_str);
break
end
end
end
% str=horzcat(str);
% Displaying final decoded string
disp('The decoded string is : ');
display(str)

% % %Program for Arithmetic encoding and decoding of an image
close all;
clear all;
clc;
I = imread('Cameraman.tif');
I = imresize(I, [3 NaN]);
disp('the pixel values are:');
disp(I);
subplot(1,2,1);
imshow(uint8(I));
title('Original image');
str=reshape(I.',1,[] ); % Convert Image from 2D to 1D
len = length(str);
fprintf('The length of the string is : %d\n', len);
u = unique(str)
disp('the unique symbols/characters are');
disp(u);
% fprintf('The unique characters are : %s\n', u);
% length of the unique characters string
len_unique = length(u);
fprintf('The length of unique character string is : %d\n', len_unique);
z = zeros(1, len_unique);
p = zeros(1, len_unique);

for i = 1 : len_unique
z(i) = length(findstr(str, u(i)));
p(i) = z(i) / len;
end
display(z);
display(p);
cpr = cumsum(p);
newcpr = [0 cpr];

display(cpr);
display(newcpr);

% % % make table till 'len_unique' size
for i = 1 : len_unique

% % % in first column we are then placing 'newcpr' values
table(i, 1) = newcpr(i);

% % % in second column we are placing 'cpr' values
table(i, 2) = cpr(i);
end

% % % Displaying the lookup table
display('The lookup table is : ')
display(table);

% % % Encoder Table

LL = 0;
UL = 1;
for i = 1 : len
for j = 1 : len_unique

% % % if the value from 'str' matches with 'u' then
if str(i) == u(j);
pos = j;
j = j + 1;

% % % displaying position of symbol in unique string
display(pos);

% % % getting the tag value of the matched character
diff_range = UL - LL;
UL = LL + (diff_range .* table(pos, 2));
LL = LL + (diff_range .* table(pos, 1));
i = i + 1;
break
end
end
end

% % % displaying tag value
tag = LL;
display(tag);
%%% DECODING %%%
%str = '';
str = [];

for i = 1 : len
for j = 1 : len_unique

% % % If tag value falls between a certain range in lookup table then
if tag (greater than or)= table(j, 1) && tag (less than) table(j, 2)
pos = j;
tag = (tag - table(pos, 1)) / p(j);

% % % Getting the matched tag value character
decoded_str = u(pos);

% % % Image pixel values concatenating 'decoded_str' into 'str'
str = horzcat(str, decoded_str);
break
end
end
end
% str=horzcat(str);
% % % Displaying final decoded image pixel values
display(str)
DD=uint8(str);
Restore=reshape(DD,3,3);
subplot(1,2,2);
imshow(Restore.');
title('Decoded Image');