Reading binary files with fread

Question

jnaumann 2013-12-10

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https://ww2.mathworks.cn/matlabcentral/answers/109300-reading-binary-files-with-fread

回答： Image Analyst 2013-12-10

Hi everyone,

I am trying to read a signal from a binary file. After lots of head scratching I have found a way of doing this. This is my current code.

fid=fopen(filename);
A=fread(fid,'bit8');
New1a=reshape(New1,2,numel(New1)/2);
New1a(1,:)=New1a(1,:)*0.000305176;
ispositive=New1a(1,:)>=0;
New1a(1,ispositive)=(New1a(1,ispositive))+(New1a(2,ispositive)*0.078125056);
New1a(1,~ispositive)=(New1a(1,~ispositive))+((New1a(2,~ispositive)+1)*0.078125056);

Although this works, the method seems a bit convoluted. Have I missed a trick somewhere and is there a easier (and possibly quicker) way of doing the same thing? Here the 0.000305176 is the resolution and the signal range is +/-10V.

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Answer 1

Image Analyst 2013-12-10

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You don't need to do all that. Just read it in as a 2D array initially. Here, see this snippet from my code:

  % Read in image2D image data
  % Get original, full-sized 2-D slice.
  % Note: fread() requires that x_size and y_size be doubles.
  % Note: fread() will return a 2D array if you pass in a 2D array for the number of bytes, as in [x_size y_size].
  if stHeader.BytesPerVoxel == 1
    oneSlice = fread(fileHandle, [x_size y_size], '*uint8');
  elseif stHeader.BytesPerVoxel == 2
    oneSlice = fread(fileHandle, [x_size y_size], '*int16'); % It will be a 2D array after this.
  else
    error('Unsupported BytesPerVoxel %d', stHeader.BytesPerVoxel);
  end