Matlab to write binary files?
4 次查看(过去 30 天)
显示 更早的评论
I am using an old dos program that states in its documentation:
input files (*._IN) are in binary Format. They cannot be edited in a text editor (e.g. Notepad) without being corrupted.
I know that with matlab I can write to binary files using fwrite, but how do I follow the format that the dos program documentation lists:
char identifier[7] = "dos 00"; // input file identifier (Text)
char version[5]="1.02 00"; // Program version (Text)
short int [2 bytes] end_line; // Total number of input file lines (short int, 0x0008, shows
// up in the file as 08 00)
char description[56] = (description line in program input file editor); // description (Text)
struct input_data{ // This block is repeated for "end_line"
char process[12]; // Process (Text) (see program manual for text strings)
char sin_string[9]; // Starting index (Text)
char units_sin[5]; // Starting index units (Text)
char ein_string[9]; // Ending index (Text)
char units_ein[5]; // Ending index units (Text)
char time_string[7]; // Time of process (Text)
char units_time[4]; // Units for time of process (Text)
};
nulls at end of each
each line is input data structure
What do the numbers in [] mean and how can i replicate this structure in matlab to generate *IN files?
0 个评论
回答(2 个)
Walter Roberson
2016-5-31
The numbers in [] indicate array sizes. So for example,
char identifier[7] = "dos 00"
means that identifier is an array of 7 char and it is to be assigned the initial value ['d', 'o', 's', ' ', '0', '0', char(0)] . Here char(0) is a binary 0 not the character '0'. Every C string is terminated with a binary 0.
The line
char version[5]="1.02 00"; // Program version (Text)
is a problem. It says that 5 characters are to be reserved for version but then it tries to initialize with 8 characters, ['1', '.', '0', '2', ' ', '0', '0', char(0)] . Depending on the exact order that the code executes in, that could end up corrupting your executable. It would make sense if it had been "1 00" or "1 02" or "1.02", but not what it is now.
"short int" corresponds to int16. The comment that 0x0008 shows up in the file as 08 00 tells you that binary values must be written in "little endian" format.
Store your data in a structure named input_data with fields named process, sin_string, units_sin, ein_string, units_ein, time_string, units_time . Do not worry about getting the length of each string exactly right, in that the code below will automatically chop or pad the values as necessary. The code takes care of the null terminator that is part of every C string.
RowV = @(C) reshape(C, 1, []);
FirstN = @(C, N) C(1:min(N,end));
ZPadTo = @(C, N) [C, zeros(1, N - length(C), 'uint8')];
CString = @(C, N) ZPadTo( FirstN(RowV(uint8(C)), N-1), N );
identifier = 'dos 00';
version = '1.02 00'; %this is going to get chopped to '1.02'
end_line = int16(length(input_data));
description = 'Some Description';
fid = fopen('YourNewFile.IN', 'w', 'ieee-le');
fwrite(fid, CString(identifier,7));
fwrite(fid, CString(version,5));
fwrite(fid, end_line, '*int16');
fwrite(fid, CString(description,56));
for IDX = 1 : length(input_data)
this = input_data(IDX);
fwrite(fid, CString(this.process, 12));
fwrite(fid, CString(this.sin_string, 9));
fwrite(fid, CString(this.units_sin, 5));
fwrite(fid, CString(this.ein_string, 9));
fwrite(fid, CString(this.units_ein, 5));
fwrite(fid, CString(this.time_string, 7));
fwrite(fid, CString(this.units_time, 4));
end
fclose(fid);
10 个评论
Image Analyst
2016-6-6
I don't know. What is an example of what it looks like? If the string needs to have the value of k embedded in it, then yes, you'll need to use sprintf. If it doesn't need k, then don't.
Image Analyst
2016-5-31
It can be a lot of work to write a file reader utility. I'm not going to do that for you but I can give you a function where I read some stuff out of a binary file. In this code I read a bunch of bytes from a binary file and stick the interpreted results (different things in the header that have different meanings) onto a structure as different fields of the structure, stHeader. See the comments to get an idea of what they are. Feel free to adapt this code as needed to your particular format:
% Read_RAW_Header
% Returns the image header information and some extra information
% 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.
3 个评论
Image Analyst
2016-6-7
OK - did it work? Does it produce a file that can be used by your other, old DOS program?
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Data Import and Export 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!