MATLAB: How to form bytes

digital image processing

To extract hidden data frm LSBs of image I have collected dataa as bits in an array array size is 486864×1 (It consists of 486864 bits that I retrieved) Now how to form bytes of this data? each 8 bits in this array is to represented as a byte How can I do ths????

Best Answer

uint8( D(1:8:end) * 128 + D(2,8,end) * 64 + D(3,8,end) * 32 (etc) )

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MATLAB: How to select bits form 1 byte values for sensor

Example:

>> a=uint8(132);
>> bitget(a,8:-1:5)
ans =
  1×4 uint8 row vector
   1   0   0   0
>> bitget(a,4:-1:1)
ans =
  1×4 uint8 row vector
   0   1   0   0

That is, the left-most of the 8 bits is bit number 8, and the right-most (least significant) is bit number 1. For your purposes you might want to code something like (7:-1:4)+1 to match the 7:0 numbering of your documentation.

MATLAB: How to convert data byte by byte

Do you really mean byte by byte? The variable read conatins 16 bit characters of the text as unicode, so a byte by byte conversion is:

read = '|0|01|00|5e|'
typecast(uint16(read), 'uint8')

The original text might be a ASCII text, then import it as bytes directly:

fid = fopen('packettext.txt', 'r');
if fid < 0, error('Cannot open file.'); end
bytes = fread(fid, inf, '*uint8');
fclose(fid);

Maybe you want to import the numbers and convert them from hex to decimal?

S = fileread('packettext.txt');
values = sscanf(S, '|%x', [1, inf]);

To clarify this, please post an example with input data and the wanted output.

Best Answer

Related Solutions

MATLAB: How to select bits form 1 byte values for sensor

MATLAB: How to convert data byte by byte

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