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L_SetTag

Summary

Specifies a private tag and the tagged data to be saved in a TIFF file.

Syntax

#include "l_bitmap.h"

L_LTFIL_API L_INT L_SetTag(uTag, uType, uCount, pData)

Parameters

L_UINT16 uTag

Tag to identify the data in the TIFF file. Generally, you can specify a private tag in the range of 0x8000 to 0xFFFE. However, LEADTOOLS returns an error if you use any of the following registered tags:

Value	Meaning
0x8298	Copyright comment
0x8769	General Exif comments
0x8825	Exif GPS comments

LEADTOOLS does NOT return an error if you set:

Value	Meaning
0x80A4	Annotation TIFF tag defined as ANNTAG_TIFF.

L_UINT16 uType

Tagged data type. Valid values are:

Value	Meaning
TAG_BYTE	[1] Byte.
TAG_ASCII	[2] Byte in the range of 0 to 255.
TAG_SBYTE	[6] Byte used as signed number in the range of -128 to +127.
TAG_UNDEFINED	[7] Byte, with application-defined usage.
TAG_SHORT	[3] Two bytes, unsigned.
TAG_SSHORT	[8] Two bytes, signed.
TAG_LONG	[4] Four bytes, unsigned.
TAG_SLONG	[9] Four bytes, signed.
TAG_RATIONAL	[5] Eight bytes, used as a pair of unsigned long integers, where the first number is the numerator and the second is the denominator of a fraction.
TAG_SRATIONAL	[10] Eight bytes, used as a pair of signed long integers, where the first number is the numerator and the second is the denominator of a fraction.
TAG_FLOAT	[11] Four bytes used as a floating point number.
TAG_DOUBLE	[12] Eight bytes used as a double-precision floating point number.
TAG_IFD	[13] 32-bit IFD offset.
TAG_LONG8	[16] Unsigned 64-bit integer (valid only for BigTIFF formats).
TAG_SLONG8	[17] Signed 64-bit integer (valid only for BigTIFF formats).
TAG_IFD8	[18] 64-bit IFD offset (valid only for BigTIFF formats).

L_UINT uCount

Count of data items, based on the tagged data type. For example, if the buffer size is 16 and the data type is TAG_DOUBLE, the count is 2.

L_VOID* pData

Pointer to a buffer containing the data to be saved using the tag.

Returns

Value	Meaning
SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

This function copies the data from your buffer to an internally-allocated buffer. You should free your own buffer after calling this function. Any TIFF file that you save will include the tagged data until you clear the tag. LEADTOOLS keeps a list of tags in memory. The list contains all the tags set directly (by calling L_SetTag) or indirectly (by calling L_AnnSaveTag). All these tags will be saved unless you clear them. The way to clear a tag and remove it from the list is by calling L_SetTag(uTag, 0, 0, NULL). L_SetTag(0,0,0,NULL) will remove ALL the tags from the tag list.

For general information about TIFF tags, refer to Implementing TIFF Comments and Tags.

Notes:

When LEADTOOLS saves a TIFF/Exif image that contains comments and tags, the comments and tags will be written first, followed by the image data. This order is not configurable.
To write tags to a TIFF file, use L_WriteFileTag or L_WriteFileTagMemory instead of using L_SetTag followed by L_SaveFile or L_SaveFileMemory.

Required DLLs and Libraries

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

Platforms

Win32, x64, Linux.

Example

This example specifies a tag for recording the position of a company logo on the image.
It sets the tag with L_SetTag; tests the tag with L_GetTag; then saves a TIFF file with the new tag.
For an example that reads this same tag from the file, refer to L_ReadFileTag.

L_INT SetTagExample(pBITMAPHANDLE pBitmap) 
{ 
   L_INT nRet; 
   L_TCHAR msgbuf[80];             /* buffer for the message string */ 
   L_UINT16 LogoPosition = 0x8001; /* my private tag                */ 
   L_UINT16 TagType = TAG_SSHORT;  /* tagged data type              */ 
   L_UINT32 TagCount = 4;          /* count of data items           */ 
   L_INT TagData[] = {5, 5, 24, 37}; 
   L_VOID * pTagData = &TagData;   /* pointer to the buffer containing the data */ 
 
   /* Set the tag data to be saved */ 
   nRet = L_SetTag(LogoPosition, TagType, TagCount, pTagData); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   /* Clear the variables so that we can validate the data */ 
   TagType = 0; 
   TagCount = 0; 
   TagData[0] = 0; 
   TagData[1] = 0; 
   TagData[2] = 0; 
   TagData[3] = 0; 
 
   /* Get the tag data that is ready to be saved */ 
   nRet = L_GetTag(LogoPosition, &TagType, &TagCount, pTagData); 
   if(nRet < SUCCESS) 
      return nRet; 
 
   /* Display a message showing the data */ 
   if ((TagType == TAG_SSHORT) && (TagCount == 4)) 
   { 
      wsprintf(msgbuf, TEXT("X = %d\nY= %d\nWidth = %d\nHeight = %d"), 
               ((L_INT  *)pTagData)[0], 
               ((L_INT  *)pTagData)[1], 
               ((L_INT  *)pTagData)[2], 
               ((L_INT  *)pTagData)[3]); 
      MessageBox (NULL, msgbuf, TEXT("Logo Position"), MB_OK); 
   } 
   /* Save the file with the tag */ 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("TEST.TIF")), pBitmap, FILE_TIF, pBitmap->BitsPerPixel, 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   /* Clear the tag from memory */ 
   nRet = L_SetTag(0, 0, 0, NULL); 
 
   return SUCCESS; 
}