-void gdcmHeader::CheckSwap()
-{
- // The only guaranted way of finding the swap code is to find a
- // group tag since we know it's length has to be of four bytes i.e.
- // 0x00000004. Finding the swap code in then straigthforward. Trouble
- // occurs when we can't find such group...
- guint32 s;
- guint32 x=4; // x : pour ntohs
- bool net2host; // true when HostByteOrder is the same as NetworkByteOrder
-
- int lgrLue;
- char * entCur;
- char deb[HEADER_LENGTH_TO_READ];
-
- // First, compare HostByteOrder and NetworkByteOrder in order to
- // determine if we shall need to swap bytes (i.e. the Endian type).
- if (x==ntohs(x))
- net2host = true;
- else
- net2host = false;
-
- // The easiest case is the one of a DICOM header, since it possesses a
- // file preamble where it suffice to look for the string "DICM".
- lgrLue = fread(deb, 1, HEADER_LENGTH_TO_READ, fp);
-
- entCur = deb + 128;
- if(memcmp(entCur, "DICM", (size_t)4) == 0) {
- filetype = TrueDicom;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:", "looks like DICOM Version3");
- } else {
- filetype = Unknown;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:", "not a DICOM Version3 file");
- }
-
- if(filetype == TrueDicom) {
- // Next, determine the value representation (VR). Let's skip to the
- // first element (0002, 0000) and check there if we find "UL"
- // - or "OB" if the 1st one is (0002,0001) -,
- // in which case we (almost) know it is explicit VR.
- // WARNING: if it happens to be implicit VR then what we will read
- // is the length of the group. If this ascii representation of this
- // length happens to be "UL" then we shall believe it is explicit VR.
- // FIXME: in order to fix the above warning, we could read the next
- // element value (or a couple of elements values) in order to make
- // sure we are not commiting a big mistake.
- // We need to skip :
- // * the 128 bytes of File Preamble (often padded with zeroes),
- // * the 4 bytes of "DICM" string,
- // * the 4 bytes of the first tag (0002, 0000),or (0002, 0001)
- // i.e. a total of 136 bytes.
- entCur = deb + 136;
- if( (memcmp(entCur, "UL", (size_t)2) == 0) ||
- (memcmp(entCur, "OB", (size_t)2) == 0) )
- {
- filetype = ExplicitVR;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:",
- "explicit Value Representation");
- } else {
- filetype = ImplicitVR;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:",
- "not an explicit Value Representation");
- }
-
- if (net2host) {
- sw = 4321;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:",
- "HostByteOrder != NetworkByteOrder");
- } else {
- sw = 0;
- dbg.Verbose(1, "gdcmHeader::CheckSwap:",
- "HostByteOrder = NetworkByteOrder");
- }
-
- // Position the file position indicator at first tag (i.e.
- // after the file preamble and the "DICM" string).
- rewind(fp);
- fseek (fp, 132L, SEEK_SET);
- return;
- } // End of TrueDicom
-
- // Alas, this is not a DicomV3 file and whatever happens there is no file
- // preamble. We can reset the file position indicator to where the data
- // is (i.e. the beginning of the file).
- rewind(fp);
-
- // Our next best chance would be to be considering a 'clean' ACR/NEMA file.
- // By clean we mean that the length of the first tag is written down.
- // If this is the case and since the length of the first group HAS to be
- // four (bytes), then determining the proper swap code is straightforward.
-
- entCur = deb + 4;
- // We assume the array of char we are considering contains the binary
- // representation of a 32 bits integer. Hence the following dirty
- // trick :
- s = *((guint32 *)(entCur));
+gdcmHeader::gdcmHeader( std::string const & filename,
+ bool exception_on_error,
+ bool enable_sequences,
+ bool ignore_shadow ):
+ gdcmDocument( filename,
+ exception_on_error,
+ enable_sequences,
+ ignore_shadow )
+{
+ // for some ACR-NEMA images GrPixel, NumPixel is *not* 7fe0,0010
+ // We may encounter the 'RETired' (0x0028, 0x0200) tag
+ // (Image Location") . This Element contains the number of
+ // the group that contains the pixel data (hence the "Pixel Data"
+ // is found by indirection through the "Image Location").
+ // Inside the group pointed by "Image Location" the searched element
+ // is conventionally the element 0x0010 (when the norm is respected).
+ // When the "Image Location" is absent we default to group 0x7fe0.