S-Box with encryption image

Hi .......

there are problem in time for encryption image by s-bos (16*16) GF, how are reduce time execution for this code ,

note : I use RGB for encryption .

x = dec2bin(layer_image(i,j),8);
l = x(1, 1 : 4);
r = x(1, 5 : 8);
ld = bin2dec(l); % row
rd = bin2dec(r); % column
layer_image(i,j)=SBox(ld+1,rd+1);

Answer 1

[Aishwarya]

x = dec2bin(layer_image(i,j),8);
l = x(1, 1 : 4);
r = x(1, 5 : 8);
ld = bin2dec(l); % row
rd = bin2dec(r); % column
layer_image(i,j)=SBox(ld+1,rd+1);

[Walter Roberson]

What difference is there between this and what was already posted?