MATLAB: Alternate method for bin2dec function

binary matrix to decimal matrix without bin2dec

i m looking for an alternate method for bin2dec conversion to speed up my code. bin2dec functions takes 2.5 to 3 sec as run time.Is there any solution. Here is my code:
tic
img = randi([0, 255], 256, 256);
y=dec2bin(img(:),8);
I=reshape(y,256,2048);
P1=reshape(bin2dec(num2str(reshape(I, 65536, []))), 256, 256);
toc
Elapsed time is 1.494633 seconds.
selftime of bin2dec-----1.420 s
Thanks in advance

Best Answer

You can create a lean version of dec2bin:
function x = myBin2Dec(s)
% Lean version of Matlab's BIN2DEC, see: help bin2dec
n     = size(s, 2);
v     = s - '0'; 
twos  = pow2(n-1:-1:0);
x     = v * twos.';
This reduces the runtime from 0.102 to 0.048 seconds and dec2bin is the bottleneck - you know how to create a lean version now.
I cannot imagine how you get 1.5 seconds. My machine is an old 2.3GHz Core2Duo. Perhaps you have a clear all before and the time is required to reload the files from the disk?
Similar to Steven's question: What is the purpose of the code? I assume that there is a faster version without the conversion to the binary strings.
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