leadfiletag

LEADFILETAG

typedef struct _LEADFILETAG
{
   L_UINT16 uTag;
   L_UINT16 uType;
   L_UINT uCount;
   L_UINT uDataSize;
   L_SIZE_T uDataOffset;
}LEADFILETAG, *pLEADFILETAG;

The LEADFILETAG structure contains information about a file tag or Geo Key. A pointer to an array of this structure is obtained by the L_ReadFileTags and L_ReadFileGeoKeys functions.

Member	Description
uTag	When used with the L_ReadFileTags function, the ID of this tag. Examples of registered tags are:
	Value	Meaning
	0x8298	Copyright comment
	0x8769	General Exif comments
	0x8825	Exif GPS comments
	When used with the L_ReadFileGeoKeys function, the ID of this Geo key. Values of the GeoKey ID range between 0 and 65535. Possible ranges are:
	Range	Meaning
	0..1023	GeoTIFF configuration keys
	1024..2047	Do not use; reserved for future use
	2048..3071	Geographic/Geocentric CS Parameter Keys
	3072..4095	Projected CS Parameter Keys
	4096..5119	Vertical CS Parameter keys
	5120..32767	Reserved
	32768..65535	Private use to store your own data
uType	When used with L_ReadFileTags, the 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.
	When used with L_ReadFileGeoKeys, the type of GeoKey to set. This indicates whether the data pointed to by ppData is SHORT, DOUBLE or ASCII. Possible values are:
	Value	Meaning
	TAG_ASCII	[2] The data pointed to by pData is an array of ASCII bytes.
	TAG_SHORT	[3] The data pointed to by pData is an array of SHORT values (2 bytes each).
	TAG_DOUBLE	[12] The data pointed to by pData is an array of floating points in DOUBLE format (8 bytes each).
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.
uDataSize	The number of bytes in the data items.
uDataOffset	Byte offset into the ppData variables where the data for this item starts. To read the data for this item, you can use pItemData = (ppData + uDataOffset)

Comments

pLEADFILETAG is a pointer to a LEADFILETAG structure. Where the function parameter type is pLEADFILETAG, you can declare a LEADFILETAG variable, update the structure's fields, and pass the variable's address in the parameter. Declaring a pLEADFILETAG variable is necessary only if your program requires a pointer.

Pass an address to pLEADFILETAG to L_ReadFileTags or L_ReadFileGeoKeys to read all the tags or geo keys stored in an image file. These function will allocate this pointer with an array of pLEADFILETAG structures, one for each item found. When you are done using the pLEADFILETAG pointer, you must pass it to the L_FreeFileTags to free the allocated memory.