how use parfor for image encryption

Hi .....

I am trying to write this code in parallel but I couldn't do that :

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [layer_image] = Encryption_SBOX(layer_image,SBox) 
[rows,cols,~] = size(layer_image);

%upperLeft
STARTblockImage1_rows=1;
STARTblockImage1_cols=1;
ENDblockImage1_rows=floor(rows/2);
ENDblockImage1_cols=floor(cols/2);
%upperRight
% STARTblockImage2_rows=1;
STARTblockImage2_cols=floor(cols/2);
% ENDblockImage2_rows=floor(rows/2);
% ENDblockImage2_cols=cols;
%lowerLeft
STARTblockImage3_rows=floor(rows/2);
% STARTblockImage3_cols=1;
% ENDblockImage3_rows=rows;
% ENDblockImage3_cols=floor(cols/2);
% lowerRight5
STARTblockImage4_rows=floor(rows/2);
STARTblockImage4_cols=floor(cols/2);
% ENDblockImage4_rows=rows;
% ENDblockImage4_cols=cols;


BZ=16; % block size 
% flipfiop=0; 
for i=STARTblockImage1_rows:BZ:ENDblockImage1_rows0
   for j=STARTblockImage1_cols:BZ:ENDblockImage1_cols
        iblock=i;
        while(iblock<=i+BZ)&&(iblock<=ENDblockImage1_rows)
            jblock=j;
            while(jblock<=j+BZ)&&(jblock<=ENDblockImage1_cols)
            %upperLeft
             x = dec2bin(layer_image(iblock,jblock),8);
             x = dec2bin(Temp1(i,j),8);
             l = x(1, 1 : 4);
             r = x(1, 5 : 8);
             ld = bin2dec(l); % row
             rd = bin2dec(r); % column
             layer_image(iblock,jblock)=SBox(ld+1,rd+1);
             
%                layer_image(iblock,jblock)=flipfiop;
             upperRight 
             if ((jblock+STARTblockImage2_cols)<=cols)
             x = dec2bin(layer_image(iblock,(jblock+STARTblockImage2_cols)),8);
             l = x(1, 1 : 4);
             r = x(1, 5 : 8);
             ld = bin2dec(l); % row
             rd = bin2dec(r); % column
             layer_image(iblock,(jblock+STARTblockImage2_cols))=SBox(ld+1,rd+1);
             else
               disp(jblock+STARTblockImage2_cols); 
             end
          %lowerLeft
          x = dec2bin(layer_image(iblock+STARTblockImage3_rows,jblock),8); 
          l = x(1, 1 : 4);
          r = x(1, 5 : 8);
          ld = bin2dec(l); % row
          rd = bin2dec(r); % column
          layer_image(iblock+STARTblockImage3_rows,jblock)=SBox(ld+1,rd+1);
          %lowerRight
          x = dec2bin(layer_image(iblock+STARTblockImage4_rows,jblock+STARTblockImage4_cols),8);
          l = x(1, 1 : 4);
          r = x(1, 5 : 8);
          ld = bin2dec(l); % row
          rd = bin2dec(r); % column
          layer_image(iblock+STARTblockImage4_rows,jblock+STARTblockImage4_cols)=SBox(ld+1,rd+1);
             jblock=jblock+1;  
            end
        iblock=iblock+1;
       end
    end
    
end

[Walter Roberson]

             x = dec2bin(layer_image(iblock,jblock),8);
             x = dec2bin(Temp1(i,j),8);

What is the purpose of the first assignment there, if you are going to overwrite all of x in the second assignment?

[Walter Roberson]

Which variable are you trying to parfor over?

[omar A.alghafoor]

I rewrite above code :

function [layer_image] = Encryption_SBOX(layer_image,SBox) 
[rows,cols,~] = size(layer_image);

%upperLeft
STARTblockImage1_rows=1;
STARTblockImage1_cols=1;
ENDblockImage1_rows=floor(rows/2);
ENDblockImage1_cols=floor(cols/2);
%upperRight
STARTblockImage2_rows=1;
STARTblockImage2_cols=floor(cols/2)+1;
ENDblockImage2_rows=floor(rows/2);
ENDblockImage2_cols=cols;
%lowerLeft
STARTblockImage3_rows=floor(rows/2)+1;
STARTblockImage3_cols=1;
ENDblockImage3_rows=rows;
ENDblockImage3_cols=floor(cols/2);
% lowerRight5
STARTblockImage4_rows=floor(rows/2)+1;
STARTblockImage4_cols=floor(cols/2)+1;
ENDblockImage4_rows=rows;
ENDblockImage4_cols=cols;


 % block size 
% flipfiop=0; 
    %parparing buffer for rows in 4 blocks
    Temp1=layer_image(1,floor(cols/2));
    Temp2=layer_image(1,floor(cols/2)+1:cols);
    Temp3=layer_image(floor(rows/2)+1,floor(cols/2));
    Temp4=layer_image(floor(rows/2)+1,cols);
    
    
for i=STARTblockImage1_rows:ENDblockImage1_rows
    Temp1=layer_image(i,ENDblockImage1_cols);
    Temp2=layer_image(i,STARTblockImage2_cols:ENDblockImage2_cols);
    Temp3=layer_image(STARTblockImage3_rows+i,ENDblockImage1_cols);
    Temp4=layer_image(STARTblockImage4_rows+i,STARTblockImage1_cols+1:ENDblockImage4_cols);
   parfor j=STARTblockImage1_cols:ENDblockImage1_cols
            %upperLeft
             x = dec2bin(Temp1(i,j),8);
             l = x(1, 1 : 4);
             r = x(1, 5 : 8);
             ld = bin2dec(l); % row
             rd = bin2dec(r); % column
             Temp1(i,j)=SBox(ld+1,rd+1);
%              upperRight 
             x = dec2bin(Temp2(i,j),8);
             l = x(1, 1 : 4);
             r = x(1, 5 : 8);
             ld = bin2dec(l); % row
             rd = bin2dec(r); % column
             Temp2(i,j)=SBox(ld+1,rd+1);
%           %lowerLeft
          x = dec2bin(Temp3(i,j),8);
          l = x(1, 1 : 4);
          r = x(1, 5 : 8);
          ld = bin2dec(l); % row
          rd = bin2dec(r); % column
          Temp3(i,j)=SBox(ld+1,rd+1);
% %           %lowerRight
          x = dec2bin(Temp4(i,j),8);
          l = x(1, 1 : 4);
          r = x(1, 5 : 8);
          ld = bin2dec(l); % row
          rd = bin2dec(r); % column
          Temp4(i,j)=SBox(ld+1,rd+1);
   end
   
    layer_image(i,ENDblockImage1_cols)=Temp1;
    layer_image(i,STARTblockImage2_cols:ENDblockImage2_cols)=Temp2;
    layer_image(STARTblockImage3_rows+i,ENDblockImage1_cols)=Temp3;
    layer_image(STARTblockImage4_rows+i,STARTblockImage1_cols+1:ENDblockImage4_cols)=Temp4;
end
end 

but there are error :

Error using test_nested_parallel (line 65)

Index in position 2 exceeds array bounds (must not exceed 1).

I think because temp( 1or others)

Answer 1

[Walter Roberson]

%                layer_image(iblock,jblock)=flipfiop;
             upperRight 

You do not have any function or variable named upperRight

[omar A.alghafoor]

yes . but not run the code

I want divided image layer ( R,G,B) and perform nested parallel , but each layer( such as R or others ) must perform parfor with 4 blocks at time

[Walter Roberson]

If you expect an RGB image then why are you using

    Temp1=layer_image(1,floor(cols/2));

which would be for accessing a grayscale or colormap image?

Consider

   Temp1=layer_image(1,floor(cols/2),:); 

However, if you are only passing in one color pane at a time, then

   [rows,cols,~] = size(layer_image);

confuses the issue -- it would not technically be wrong, but it would lead the reader to expect that there is a 3rd dimension.

[omar A.alghafoor]

thank you , will try this solution.