A Computational Introduction to Digital Image Processing, 2nd Edition

Images Files and File Types 39

MATLAB/Octave

function hexdump(filenm, n)

% hexdump(filenm, n)

% Print the first n bytes of a file in hex and ASCII.

fid = fopen(filenm, ’r’);

if (fid<0) disp([’Error

opening ’,filenm]); return; end;

nread = 0;

while (nread < n)

width = 16;

[A,count] = fread(fid, width, ’uchar’);

nread = nread + count;

if (nread>n) count = count - (nread-n); A = A(1:count); end;

hexstring = repmat(’ ’,1,width

*

2);

hexstring(1:2

*

count) = sprintf(’%02x’,A);

hexdisp = repmat(’

’,1,40);

for

i = 1:idivide(count,2)

hexdisp(5

*

i-4:5

*

i-1) = hexstring(4

*

i-3:4

*

i);

end

ascstring = repmat(’.’,1, count);

idx = find(double(A)>=32 & double(A)<=126);

ascstring(idx) =