Import binary data to array
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I have a file (sensor.lobe)(342848 bytes) containing binary data with the following data format:
Lokal ID 4 byte signed int
data1 8 byte double
data2 8 byte double
data3 8 byte double
data4 4 byte unsigned int
little endian
How do I import, for example, data1 into an array?
I tried this:
fid = fopen('sensor.lobe','r', 'l');
status = fseek(fid,4,'bof');
A = fread(fid, 8,'double', 'l');
The result does not make sense:
A =
1.0e-314 *
0.5300
0.5305
0.5308
0.5310
Can anybody tell me what I am doing wrong?
回答（3 个）
José-Luis
2013-1-31
status = fseek(fid,3,'bof');
Image Analyst
2013-1-31
编辑：Image Analyst
2013-1-31
Here's an example of how I read a binary header with a variety of data types:
% Read_RAW_Header
% Returns the image header information and some extra information
% for our custom-defined raw image file.
% Usage: stHeader = Read_RAW_Header(filename)
% Input
% filename - RAW format file name
% Output
% stHeader - header structure containing information on the data
% Header is 44 bytes.
% The header of an RAW file will look something like this:
% stHeader.TotalVoxels: Array size - total size of the array (not the whole file) - number of voxels.
% stHeader.NumberOfDimensions: Number of dimensions - 3 for a 3D image.
% stHeader.x_size: Size (number of voxels) in the X direction.
% stHeader.y_size: Size (number of voxels) in the Y direction.
% stHeader.z_size: Size (number of voxels) in the Z direction.
% stHeader.XStart: Position of the center of the first pixel in the X direction - it's 0.
% stHeader.YStart: Position of the center of the first pixel in the Y direction - it's 0.
% stHeader.ZStart: Position of the center of the first pixel in the Z direction - it's 0.
% stHeader.XEnd: Position of the center of the last pixel in the X direction - it's voxelWidth * (sizeX - 1).
% stHeader.Yend: Position of the center of the last pixel in the Y direction - it's voxelWidth * (sizeY - 1).
% stHeader.ZEnd: Position of the center of the last pixel in the Z direction - it's voxelWidth * (sizeZ - 1).
% Following the header in the data file, are the voxel values, but of course we do not return these in the header.
%
% I also add these fields to the returned header argument:
% stHeader.HeaderSize = 44;
% stHeader.BytesPerVoxel
% stHeader.FileSizeInBytes
% stHeader.DataSizeInBytes
% stHeader.Endian
% stHeader.EndianArg
%
% Example usage:
% fullFileName_RAW = fullfile(cd, 'SimulatedData_Distance.RAW')
% stHeader = Read_RAW_Header(fullFileName_RAW)
%
%------------------------------------------------------------------------------
function stHeader = Read_RAW_Header(fullFilename)
% Check syntax. Must have at least one input argument, the full filename.
if (nargin ~= 1)
error('Usage: stHeader = Read_RAW_Header(fullFilename)');
end
if (ischar(fullFilename)~=1)
error('Requires a string filename as an argument.');
end
% These aren't in the header specification for this type of file,
% but other formats use it and it's a useful thing to add to the header.
stHeader.Endian = 'Big';
stHeader.EndianArg = 'ieee-be';
% Open the file for reading.
fileHandleID = fopen(fullFilename, 'rb', stHeader.EndianArg);
if (fileHandleID == -1)
error(['Error opening ', fullFilename, ' for input.']);
end
% Go to the beginning of the file.
% Shouldn't be necessary, but can't hurt.
fseek(fileHandleID, 0, 'bof');
% Read the total number of voxels in the image.
% Read bytes 1-4.
stHeader.TotalVoxels = fread(fileHandleID, 1, '*int32');
% Note: this may be unreliable, and can be zero!
% Better to take the x, y, and z sizes and multiply them together.
% The next 4 bytes are the number of dimensions - 2 or 3.
% Read bytes 5-8.
stHeader.NumberOfDimensions = fread(fileHandleID, 1, 'int32');
% Read in the dimensions for the different directions.
% They'll be in bytes 9-20.
stHeader.x_size = fread(fileHandleID, 1, '*int32');
stHeader.y_size = fread(fileHandleID, 1, '*int32');
stHeader.z_size = fread(fileHandleID, 1, '*int32');
stHeader.TotalVoxels = stHeader.x_size * stHeader.y_size * stHeader.z_size;
% Read in the position of the center of the first pixel.
% They'll be in bytes 21-32.
stHeader.XStart = fread(fileHandleID, 1, '*float');
stHeader.YStart = fread(fileHandleID, 1, '*float');
stHeader.ZStart = fread(fileHandleID, 1, '*float');
% Read in the position of the center of the last pixel.
% They'll be in bytes 33-44.
stHeader.XFieldOfView = fread(fileHandleID, 1, '*float');
stHeader.YFieldOfView = fread(fileHandleID, 1, '*float');
stHeader.ZFieldOfView = fread(fileHandleID, 1, '*float');
% Note: the fields of view are based on (pixel center) - to - (pixel center).
% Calculate the voxel width.
stHeader.VoxelWidth = stHeader.XFieldOfView / single(stHeader.x_size - 1);
% Assign some other useful information.
% It's not in the header but may come in useful anyway.
% Assign the bytes per voxel.
%fileInfo = imfinfo(fullFilename); % Note: doesn't work!
% fileSizeInBytes = fileInfo.FileSize;
% This works:
fileInfo = dir(fullFilename);
% MATLAB returns the information in a structure with fields:
% name
% date
% bytes
% isdir
% datenum
stHeader.HeaderSize = 44;
fileSizeInBytes = fileInfo.bytes;
dataSizeInBytes = double(fileSizeInBytes) - double(stHeader.HeaderSize);
stHeader.BytesPerVoxel = int32(round(dataSizeInBytes / double(stHeader.TotalVoxels)));
stHeader.FileSizeInBytes = fileSizeInBytes;
stHeader.DataSizeInBytes = dataSizeInBytes;
% Close the file.
fclose(fileHandleID); % Close the file.
I see that I used '*float' and you used 'double' with no *.
You want to import 1 double only, not 8.
Alternatively you can read the data instead of skipping them:
fid = fopen('sensor.lobe','r', 'l');
LokalID = fread(fid, 1, 'int32');
data1 = fread(fid, 1, 'double');
data2 = fread(fid, 1, 'double');
data3 = fread(fid, 1, 'double');
data4 = fread(fid, 1, 'uint32');
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