Rashen Fernando - Zig Zag Scan

Step 5- Develop an algorithm to scan zig zag

function [i,j] = sort_indices(n,macroblock_size)

a = macroblock_size - abs(n-macroblock_size);

b = n-macroblock_size;

i=[];j=[];

if(~rem(n,2)) %if n even i is ascending j is descending

%--------------------------------------------------------------------------

if(b<=0) %b<=0 range is 1 to a else range begins from macroblock_size

for m=1:a

i = [i m];

j = [m j];

end

else

for m = macroblock_size-(a-1):macroblock_size

i = [i m];

j = [m j];

end

%-------------------------------------------------------------------------

else

%-------------------------------------------------------------------------

if(b<=0) %b<=0 range is 1 to a else range begins from macroblock_size

for m=1:a

i = [m i];

j = [j m];

end

else

for m = macroblock_size-(a-1):macroblock_size

i = [m i];

j = [j m];

end

%--------------------------------------------------------------------------

end

function [row_ind_vec,column_ind_vec] = zigzag(x)

row_ind_vec = [];

column_ind_vec = [];

for n = 1:size(x,1)*2-1

[i,j]=sort_indices(n,size(x,1));

row_ind_vec = [row_ind_vec i];

column_ind_vec = [column_ind_vec j];

end

Now that indices of the elements when an 4x4 macroblock is zig zag scanned are obtained as expected (refer above notes) we can apply this for the whole image considering every macroblock to obtain the stream of values..

function one_img_vector = oneMblockVec(image,macroblock_size,row_ind_vec,column_ind_vec)

one_img_vector ={};

for y = 1:size(image,1)

for x = 1:size(image,2)

macroblock = cell2mat(image(y,x));

temp_block=[];

for a = 1:size(row_ind_vec,2)

temp1 = row_ind_vec(a);

temp2 = column_ind_vec(a);

%one_img_vector = [one_img_vector macroblock(temp1,temp2) ];

temp_block=[temp_block macroblock(temp1,temp2)];

end

one_img_vector =[one_img_vector {temp_block}];

end