L_ReadFileGeoKey
#include "l_bitmap.h"
L_INT EXT_FUNCTION L_ReadFileGeoKey(pszFile, uTag, puType, pCount, pData, pLoadOptions)
/* input file name */ | |
L_UINT16 uTag; |
/* GeoKey to identify the data in the GeoTIFF file */ |
/* pointer to a variable */ | |
/* pointer to a variable */ | |
/* pointer to the buffer for the data */ | |
pLOADFILEOPTION pLoadOptions; |
/* pointer to optional extended load options */ |
Gets the specified GeoKey data from a TIFF file. This function is provided to support GeoKeys that you define.
Parameter |
Description |
|
pszFile |
Character string that contains the input file name to load. |
|
uTag |
GeoKey ID that you specified by calling L_SetGeoKey function. 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 – use to store your own data. |
puType |
Pointer to a variable to be updated with the GeoKey type. 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). |
puCount |
Pointer to the variable to be updated with the number of items required for the pData buffer. Note that this is not the required number of bytes. The required number of bytes will be (*puCount) * number of bytes per value (1 for ASCII, 2 for SHORT, 8 for DOUBLE). If pData passed as NOT NULL, this variable will be updated with the count of data items. |
|
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. |
|
pLoadOptions |
Pointer to optional extended load options. Pass NULL to use the default load options. |
Returns
SUCCESS |
The function was successful. |
< 1 |
An error occurred. Refer to Return Codes. |
Comments
You can use this function to obtain the GeoKey data from a particular file.
It is often convenient to call this function twice, as follows:
1. |
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. |
2. |
Allocate the buffer. |
3. |
Call the function the second time, passing a pointer to your buffer in the pData parameter. |
The most efficient way of reading the GeoKeys in a file is to enumerate them with L_EnumFileGeoKeys and then read each GeoKey with L_ReadFileGeoKey.
For more information about GeoKeys, refer to Implementing GeoKeys (GeoTIFF tags).
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
Windows 95 / 98 / Me, Windows 2000 / XP.
See Also
Functions: |
L_SetGeoKey, L_GetGeoKey, L_WriteFileGeoKey, L_WriteFileMetaData, L_EnumFileGeoKeys, L_SaveFile, L_SaveBitmap |
Topics: |
|
|
|
|
Example
For an example, refer to L_WriteFileGeoKey function.