In This Topic ▼

L_GetTag

Summary

Gets the data that is ready to be saved as tagged data in a TIFF file. This lets you see the data that was specified with the L_SetTag function.

Syntax

#include "l_bitmap.h"

L_LTFIL_API L_INT L_GetTag(uTag, pType, pCount, pData)

Parameters

L_UINT16 uTag

Tag to identify the data in the TIFF file. Use the same tag that you specified in the L_SetTag function.

L_UINT16* pType

Address of the variable to be updated with the tagged data type. The following are possible values:

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* pCount

Address of the variable to be updated with the count of data items. The count is based on the tagged data type. For example, if the count is 2 and the data type is TAG_DOUBLE, the required buffer size is 16.

L_VOID* pData

Pointer to the buffer to be updated with the data. You can pass NULL if you want to use this function's return value to determine the required buffer size.

Returns

Value	Meaning
>0	Length of the tagged data, in bytes.
<= 0	An error occurred. Refer to Return Codes.

Comments

It is often convenient to call this function twice, as follows:

Call the function the first time, specifying NULL in the pData parameter, and using the return value to determine the required size of the buffer.
Allocate the buffer.
Call the function the second time, passing a pointer to your buffer in the pData parameter.

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

To detect whether a file has annotation information, you should call L_GetTag and see if ANNTAG_TYPE is present.