LDicomDS::GetFirstElement

#include "Ltdic.h"

pDICOMELEMENT LDicomDS::GetFirstElement(pElement, bTree, bVolatile)

pDICOMELEMENT pElement;	/* pointer to a DICOMELEMENT structure */
L_BOOL bTree;	/* flag that indicates how to evaluate the Data Set */
L_BOOL bVolatile;	/* flag that indicates the type of element to retrieve */

Returns a pointer to the first item in the Data Set.

Parameter	Description
pElement	Pointer to a DICOMELEMENT structure within the Data Set. A pointer to the DICOMELEMENT structure that contains the first item in the Data Set will be returned.
bTree	Flag that indicates how the Data Set will be evaluated. Possible values are:
	Value	Meaning
	TRUE	Evaluate the Data Set as a tree.
	FALSE	Evaluate the Data Set as a list.
bVolatile	Flag that indicates the type of element to retrieve. Possible values are:
	Value	Meaning
	TRUE	Retrieve the first element, volatile or non-volatile.
	FALSE	Retrieve the first non-volatile element.

Returns

!NULL	A pointer to a DICOMELEMENT structure that contains the first item in the Data Set.
NULL	The Data Set is empty.

Comments

If the Data Set is evaluated as a tree structure, this function returns the first item on the same level as pElement with the same parent as pElement. Please note that the numbering of the items in this first illustration is arbitrary and does not imply order.

$image\GetFstTr.gif$

If the passed pointer points to :	The function returns a pointer to :
Item 1	Item 2
Item 3	Item 4
Item 5	Item 5
Item 6	Item 7
NULL	Item 2

If the Data Set is evaluated as a list, the first item in the list is returned. Please note that the numbering of the items in this illustration does indicate the order of the items when the Data Set is evaluated as a list.

$image\GetFtLst.gif$

If the passed pointer points to :	The function returns a pointer to :
NULL	Item 1
Item 12	Item 1
Item 14	Item 1
Item 22	Item 1
Item 25	Item 1

The following functions will also help you navigate the Data Set as either a tree or a list:

LDicomDS::GetLastElement

LDicomDS::GetPrevElement

LDicomDS::GetNextElement

If you evaluate the Data Set as a tree, you can also use the following functions to navigate the tree:

LDicomDS::GetRootElement

LDicomDS::GetParentElement

LDicomDS::GetChildElement

A volatile element is an element that can be changed or destroyed in the process of inserting or setting an image. A non-volatile element is an element that must be changed manually. It is not changed or destroyed by inserting or setting an image.

For example, a grayscale image has elements TAG_SMALLEST_IMAGE_PIXEL_VALUE, TAG_LARGEST_IMAGE_PIXEL_VALUE, etc. If the image is changed to a color image, these elements disappear and the following elements appear: TAG_RED_PALETTE_COLOR_LOOKUP_TABLE_DESCRIPTOR, etc. These are volatile elements since they are changed or destroyed when an image is changed or set.

To retrieve the first element that must be changed manually, i.e. is not volatile, set bVolatile to FALSE. To retrieve the first element, either volatile or non-volatile, set bVolatile to TRUE.

Required DLLs and Libraries

LTDIC

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application

See Also

Functions:	LDicomDS::GetLastElement, LDicomDS::GetPrevElement, LDicomDS::GetNextElement, LDicomDS::GetCountModule, LDicomDS::GetRootElement, LDicomDS::GetParentElement, LDicomDS::GetChildElement, LDicomDS::IsVolatileElement
Topics:	Working with Data Sets
	How to Disable the Automatic Loading of the default DICOM IOD Table

Example

This example displays in a tree control the list of elements in the Data Set.

L_VOID ShowList(CTreeCtrl *pDlg, LDicomDS *pDS)
{
   HTREEITEM       hItem;
   pDICOMELEMENT   pElement;
   pDICOMTAG       pTag;
   L_TCHAR          szUnknown[]=TEXT("Unknown");
   L_TCHAR         *p;
   pElement = pDS->GetFirstElement(NULL, FALSE, FALSE);
   while (pElement != NULL)
   {
      pTag = LDicomTag::Find(pElement->nTag);
      if (pTag != NULL)
      {
         p = pTag->pszName;
      }
      else
      {
         p = szUnknown;
      }
      hItem = pDlg->InsertItem(p, TVI_ROOT, TVI_LAST);
      pElement = pDS->GetNextElement(pElement, FALSE, FALSE);
   }
}
L_INT LDicomDS_GetFirstElementExample(CTreeCtrl *pDlg)
{
   LDicomDS *pDS;
   pDS = new LDicomDS(NULL);
   pDS->InitDS( CLASS_XA_BIPLANE_IMAGE_STORAGE_RETIRED, 0); 
   ShowList(pDlg, pDS);
   delete pDS;
   return DICOM_SUCCESS;
}