LFile::DeleteTag

#include "ltwrappr.h"

L_INT LFile::DeleteTag(nPage, uTag, uFlags, pSaveOptions)

L_INT nPage;	/* page number */
L_UINT uTag;	/* the ID of the tag that should be deleted */
L_UINT uFlags;	/* reserved for future use */
pSAVEFILEOPTION pSaveOptions;	/* pointer to optional extended save options */

Deletes a tag from a file, if the file supports tags (TIFF or Exif).

Parameter	Description
nPage	Number of the page from which the tag will be deleted. Use -1 to delete the tag from the last page. Use 1 to delete the tag from the first page.
uTag	The ID of the tag in the TIFF file. The tag IDs are between 0 and 65535.
uFlags	Reserved for future use. Pass 0.
pSaveOptions	Pointer to optional extended save options. Pass NULL to use the default save options.

Returns

SUCCESS	The function was successful.
ERROR_TAG_MISSING	The requested tag is missing.
< 1	An error occurred. Refer to Return Codes.

Comments

Note that if you pass a SAVEFILEOPTION, the PageNumber member of that structure will be ignored. The page number is indicated through the nPage parameter of this function.

If you want to delete the tag from a particular IFD in the file, set ESO_USEIFD in the SAVEFILEOPTIONS.Flags parameter and set SAVEFILEOPTIONS.IFD to the IFD in question. This function will delete tags only from the main IFDs that make up an image. Some TIFF tags are themselves SubIFDs. You can delete tags from such SubIFDs by using the SAVEFILEOPTION and specifying the IFD as above.

Notes:

1.	The LFCMP filter is used to delete the tag from all the TIFF and Exif files.
2.	Do not attempt to use this function to delete tags from inside an LFile::EnumTagsCallBack callback function. If you want to delete tags that you enumerate, use LFile::EnumTagsCallBack to add the tags to a list. Upon returning from LFile::EnumTags, you can delete all the tags from the list.
3.	You should be careful when you delete non-custom tags (tags below 32768). If you delete the wrong tag, you might corrupt the TIF file!

When you add or remove comments or tags, the comments and tags array at the end of the TIFF/Exif image file is re-written. When you modify existing comments or tags, the new value is added to the file and the IFD is modified as necessary. In all of these cases, there is no image recompression.

Required DLLs and Libraries

LTFIL

LFCMP

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:	LFile::ReadTag, LFile::WriteTag, LFileSettings::SetTag, LFileSettings::GetTag, LFile::EnumTags
Topics:	Implementing TIFF Comments and Tags
	Raster Image Functions: Maintaining File Comments and Tags

Example

The following example will delete the tag 0x8001 from page 1 of a TIFF file.

L_INT LFile__DeleteTagExample() 
{
   LFile lf ;
   LOADFILEOPTION LoadFileOption;
   L_INT nRet = 0;
   lf.SetFileName(TEXT("%UserProfile%\\My Documents\\LEADTOOLS Images\\Faces_24.tif"));
   lf.GetDefaultLoadFileOption(&LoadFileOption, sizeof(LoadFileOption));
   LoadFileOption.PageNumber = 1;
   nRet = lf.ReadTag(0x8001, NULL, NULL, NULL, &LoadFileOption) ;
   if (nRet != SUCCESS)
   {
      nRet = lf.DeleteTag(1, 0x8001, 0, NULL);
      if(nRet != SUCCESS)
         return nRet;
   }
   return SUCCESS;
}