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L_SetGeoKey

Summary

Sets the GeoKey data to be saved in a file.

Syntax

#include "l_bitmap.h"

L_LTFIL_API L_INT L_SetGeoKey (uTag, uType, uCount, pData);

Parameters

L_UINT16 uTag

ID of the GeoKey to set. Values of the GeoKey ID range between 0 and 65535. Possible ranges are:

Range	Meaning
0..1023	Do not use; reserved for future use.
1024..2047	GeoTIFF configuration keys.
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

L_UINT uType

The type of GeoKey to set. This indicates whether the data pointed to by pData 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).
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

The number of items in the pData buffer. Note that this does not describe the number of bytes. The number of bytes is uCount * number of bytes per value (1 for ASCII, 2 for SHORT, 8 for DOUBLE).

L_VOID* pData

Pointer to a buffer that contains the GeoKey data.

If the pData passed as NULL, the GeoKey data associated with uTag will be cleared; and the uType and uCount parameters will be ignored.

Returns

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

Comments

This function copies the data pointed to by pData into an internal list of buffers maintained by LTFIL. The user is responsible for freeing the buffer pointed to by pData after calling this function.

Any GeoTIFF file that you save will include the GeoKey data set until you clear the GeoKey data. To save this data to a file, save FILE_GEOTIFF files.

To clear a particular GeoKey, call:

L_SetGeoKey(uTag, 0, 0, NULL);

To clear all the GeoKeys, call:

L_SetGeoKey(0, 0, 0, NULL);

The data set will be saved in the files into 3 TIFF tags:

GeoKeyDirectoryTag: 34735 (0x87AF) this tag will store all the keys and the SHORT values.

GeoDoubleParamsTag: 34736 (0x87B0) this tag will store the DOUBLE values.

GeoAsciiParamsTag: 34737 (0x87B1) this tag will store the ASCII values.

L_SetGeoKey will overwrite any values saved for these tags previously using L_SetTag.

For more information on the various GeoKey values and for links to the GeoTIFF specification, refer to Implementing GeoKeys (GeoTIFF tags).

You can get the last value set with L_SetGeoKey by using L_GetGeoKey.

To write the GeoKey data directly to an existing file, call L_WriteFileGeoKey.

Note that LEADTOOLS does not verify the validity of the GeoKeys that you set. It is your responsibility to make sure you write correct values according to the GeoTIFF specification.

Required DLLs and Libraries

LTFIL
LFTIF
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 sets the GTModelTypeGeoKey key to the Project Coordination System value

L_INT SetGeoKeyExample(L_VOID) 
{ 
   L_INT nRet; 
   L_UINT16 uProjectCoordinationSystem = 1; 
 
   nRet = L_SetGeoKey(1024, TAG_SHORT, 1, &uProjectCoordinationSystem); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   /* Every GeoTIFF file that is saved from now on will contain this GeoKey */ 
   return SUCCESS; 
}