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R8218/private/parsegraphicsubheader20.m
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parsegraphicsubheader20.m
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function gsnitf_meta = parsegraphicsubheader20( fid, dataLength )
%PARSEGRAPHICSUBHEADER Parse the Graphic subheaders in an NITF file.
% GSNITF_META = PARSEGRAPHICSUBHEADER20
% Parse the Graphic Segment Subheader for an NITF 2.0 file.
% Copyright 2007-2008 The MathWorks, Inc.
% Initialize the graphic subheader structure
gsnitf_meta = struct([]);
fields = {'SY', 'FilePartType', 2
'SID', 'SymbolID', 10
'SNAME', 'SymbolName', 20
'SSCLAS', 'SymbolSecurityClassification', 1
'SSCODE', 'SymbolCodewords', 40
'SSCTLH', 'SymbolControlAndHandling', 40
'SSREL', 'SymbolReleasingInstructions', 40
'SSCAUT', 'SymbolClassificationAuthority', 20
'SSCTLN', 'SymbolSecurityControlNumber', 20
'SSDWNG', 'SymbolSecurityDowngrade', 6};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
%SSDWNG is GSNITF_META(10) and the last item extracted in the loop above. Depending
%on its value there will be an SSDEVT
ssdwng = sscanf(gsnitf_meta(end).value, '%f');
if ssdwng == 999998
fields = {'SSDEVT', 'SymbolDowngradingEvent', 40};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
end
fields = {'ENCRYP', 'Encryption', 1
'STYPE', 'SymbolType', 1
'NLIPS', 'NumberOfLinesPerSymbol', 4
'NPIXPL', 'NumberOfPixelsPerLine' 4
'NWDTH', 'LineWidth', 4
'NBPP', 'NumberOfBitsPerPixel', 1
'SDLVL', 'DisplayLevel', 3
'SALVL', 'SymbolAttachmentLevel', 3
'SLOC', 'SymbolLocation', 10
'SLOC2', 'SecondSymbolLocation', 10
'SCOLOR', 'SymbolColor', 1
'SNUM', 'SymbolNumber', 6
'SROT', 'SymbolRotation', 3
'NELUT', 'NumberOfLUTEntries', 3};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
%DLUT -- This is the actual look-up table which I think constitutes data
% Should we expose it as metadata?
nelut = sscanf(gsnitf_meta(end).value, '%f');
if nelut ~= 0
if strcmp(scolor,'C') %Color look-up table
dlutsize = 3 * nelut;
elseif strcmp(scolor,'G') %Gray scale look-up table
dlutsize = nelut;
else
dlutsize = 0;
end
fields = {'DLUT', 'SymbolLUTData', dlutsize};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
end
fields = {'SXSHDL', 'ExtendedSubheaderDataLength', 5};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
%SXSOFL and SCSHD
sxshdl = sscanf(gsnitf_meta(end).value, '%f');
if sxshdl ~= 0
fields = {'SXSOFL', 'ExtendedSubheaderOverflow', 3
'SXSHD', 'ExtendedSubheaderData', sxshdl - 3};
gsnitf_meta = nitfReadMeta(gsnitf_meta, fields, fid);
end
%Move the cursor through the graphic data
readforwardbytes = sscanf(dataLength, '%f');
fread(fid, readforwardbytes, 'uint8=>char');
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