hdfpeek.m

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function [tagreflist, namelist, info]=hdfpeek( filename, tagref )
%HDFPEEK List object tag/ref pairs in HDF file.
%   Note: HDFPEEK has been grandfathered. Use IMFINFO, IMREAD,
%   and IMWRITE instead.
%
%   [TAGREF,NAME,INFO]=HDFPEEK( 'filename' ) scans an HDF file
%   and returns a list of tag/reference no. pairs for image
%   groups in the file.  TAGREF is an Nx2 matrix where N is the
%   number of images found, and each row contains the tag and
%   reference no. for an image in the file.  NAME returns a
%   matrix of strings containing the group names corresponding to
%   the tags of the images, and INFO contains a corresponding
%   list of scalars denoting the image depth (8 for binary,
%   intensity, and indexed images, 24 for RGB images, -1 for
%   unknown). 
%
%   [TAGREF,NAME,INFO]=HDFPEEK( 'filename', [GROUPTAG GROUPREF] )
%   returns a list of data objects in the specified Raster Image
%   Group, using the same output format as given above, except
%   INFO will be a single scalar instead of a list of scalars.  
%
%   See also IMFINFO, IMREAD, IMWRITE.

%   Author: J.M. Winograd   7-93
%   Revised: Steven L. Eddins, May 1996
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 5.5 $  $Date: 1997/11/24 15:35:04 $

error( nargchk( 1, 2, nargin ) );

if (~isstr(filename))
    error( 'FILENAME must be a string.' );
end

% Find full filename
fid = fopen(filename);
if fid == -1, error(['File ',filename,' not found.']); end
fname = fopen(fid); fclose(fid);

if nargin == 1
    [tagreflist, namelist, info] = TagSearch( fname );
else
    if (tagref(1,1) ~= 306)
        error('Unsupported or invalid group tag');
    end
    [tagreflist, namelist, info] = RIGSearch( fname, tagref(1,2) );
end


%%%
%%% TagSearch --- find and return info about RIG tags in file
%%%
function [tagreflist, namelist, info] = TagSearch(fname)

DFTAG_RIG = 306;
DFTAG_ID = 300;
DFREF_WILDCARD = 0;

% restart HDF system
hdf('DFR8', 'restart');
hdf('DF24', 'restart');

file_id = hdf('H', 'open', fname, 'read', 0);
if (file_id == -1)
    error(sprintf('Could not open %s', fname));
end

% Find number of objects in file with the Raster Image Group tag
matchCount = hdf('H', 'number', file_id, DFTAG_RIG);

tagreflist = zeros(matchCount, 2);
namelist = repmat(' ', matchCount, 30);
info = zeros(matchCount, 1);

access_id = hdf('H', 'startread', file_id, DFTAG_RIG, DFREF_WILDCARD);
status = access_id;

for k = 1:matchCount
    if (status == -1)
        hdf('H', 'endaccess', access_id);
        hdf('H', 'close', file_id)
        error(hdf('HE', 'string', hdf('HE', 'value', 1)));
    end
    [junk, junk, ref, numbytes, junk, junk, junk, junk, status] = ...
            hdf('H', 'inquire', access_id);
    if (status == -1)
        hdf('H', 'endaccess', access_id);
        hdf('H', 'close', file_id)
        error(hdf('HE', 'string', hdf('HE', 'value', 1)));
    end

    tagreflist(k,:) = [DFTAG_RIG ref];
    
    nameString = hdf('HD', 'gettagsname', DFTAG_RIG);
    nameString = nameString(1:min(end, 30));
    namelist(k,1:length(nameString)) = nameString;
    
    memberList = hdf('H', 'read', access_id, numbytes);
    if (isempty(memberList))
        hdf('H', 'endaccess', access_id);
        hdf('H', 'close', file_id)
        error(hdf('HE', 'string', hdf('HE', 'value', 1)));
    end

    memberList = Uint16Decode(memberList);
    memberTags = memberList(1:2:end);
    memberRefs = memberList(2:2:end);
    idx = find(memberTags == DFTAG_ID);
    if (isempty(idx))
        warning('Missing DFTAG_ID in Raster Image Group');
        info(k) = -1;
        break;
    else
        idx = idx(1);  % There should be only 1, but we'll be cautious
    end

    % Find the number of components, which is stored in the DFTAG_ID record.
    access_id2 = hdf('H', 'startread', file_id, DFTAG_ID, memberRefs(idx));
    if (access_id2 == -1)
        hdf('H', 'endaccess', access_id);
        hdf('H', 'close', file_id)
        error(hdf('HE', 'string', hdf('HE', 'value', 1)));
    end
    memberList = hdf('H', 'read', access_id2, 14);
    if (isempty(memberList))
        hdf('H', 'endaccess', access_id);
        hdf('H', 'endaccess', access_id2);
        hdf('H', 'close', file_id)
        error(hdf('HE', 'string', hdf('HE', 'value', 1)));
    end
    hdf('H', 'endaccess', access_id2);

    numComponents = Uint16Decode(memberList(13:14));
    
    if (numComponents == 1)
        info(k) = 8;
    
    elseif (numComponents == 3)
        info(k) = 24;
        
    else
        info(k) = -1;
    end

    if (k < matchCount)
        status = hdf('H', 'nextread', access_id, DFTAG_RIG, ...
                DFREF_WILDCARD, 'current');
    end
    
end

hdf('H', 'endaccess', access_id);
hdf('H', 'close', file_id);


%%%
%%% RIGSearch --- return list of tags contained in Raster Image Group
%%%
function [tagrefs,names,info] = RIGSearch(fname, ref)

% HDF constants 
DFTAG_RIG = 306;
DFTAG_ID = 300;

% Restart HDF system
hdf('DFR8', 'restart');
hdf('DF24', 'restart');

file_id = hdf('H', 'open', fname, 'read', 0);
if (file_id == -1)
    error(sprintf('Could not open %s', fname));
end

access_id = hdf('H', 'startread', file_id, DFTAG_RIG, ref);
if (access_id == -1)
    hdf('H', 'close', file_id);
    error(hdf('HE', 'string', hdf('HE', 'value', 1)));
end

bytes = hdf('H', 'read', access_id, 0);
if (isempty(bytes))
    hdf('H', 'endaccess', access_id);
    hdf('H', 'close', file_id);
    error(hdf('HE', 'string', hdf('HE', 'value', 1)));
end

hdf('H', 'endaccess', access_id);

shorts = Uint16Decode(bytes);
memberTags = shorts(1:2:end);
memberRefs = shorts(2:2:end);
tagrefs = [memberTags memberRefs];

names = '';
for k = 1:length(memberTags)
    names = str2mat(names, hdf('HD', 'gettagsname', memberTags(k)));
end
names(1,:) = [];

idx = find(memberTags == DFTAG_ID);
if (isempty(idx))
    warning('Missing DFTAG_ID in Raster Image Group');
    info = -1;
    break;
else
    idx = idx(1);  % There should be only 1, but we'll be cautious
end

% Find the number of components, which is stored in the DFTAG_ID record.
access_id = hdf('H', 'startread', file_id, DFTAG_ID, memberRefs(idx));
if (access_id == -1)
    hdf('H', 'close', file_id)
    error(hdf('HE', 'string', hdf('HE', 'value', 1)));
end
memberList = hdf('H', 'read', access_id, 14);
if (isempty(memberList))
    hdf('H', 'endaccess', access_id);
    hdf('H', 'close', file_id)
    error(hdf('HE', 'string', hdf('HE', 'value', 1)));
end
hdf('H', 'endaccess', access_id);

numComponents = Uint16Decode(memberList(13:14));

if (numComponents == 1)
    info = 8;
    
elseif (numComponents == 3)
    info = 24;
    
else
    info = -1;
end

hdf('H', 'close', file_id);


%%%
%%% Uint16Decode --- turn uint8 input into uint16 integers
%%%
function out = Uint16Decode(in)

msb = double(in(1:2:end));
lsb = double(in(2:2:end));

out = bitshift(msb,8) + lsb;