#include "l_bitmap.h"
L_LTFIL_API L_INT L_GetGeoKey(uTag, puType, puCount, pData)
Gets the data that is ready to be saved as GeoKeys in a GeoTIFF file.
ID of the GeoKey to get. 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. |
Pointer to the variable to be updated with the GeoKey type. It 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). |
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 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 number of data items.
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.
Value | Meaning |
---|---|
> 0 | The length of the GeoKey data in bytes. |
0 | There is no GeoKey data with this GeoKey. |
< 0 | An error occurred. Refer to Return Codes. |
You can use this function to obtain GeoKey data that will be saved the next time you save a GeoTIFF (FILE_GEOTIFF) file.
If you want to get the GeoKey data from a particular file, use the L_ReadFileGeoKey function.
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 more information about GeoKeys, refer to Implementing GeoKeys (GeoTIFF tags).
Required DLLs and Libraries
Win32, x64, Linux.
This example gets the value set for the GTModelTypeGeoKey key.
Note that the example can be simpler by not allocating memory because this particular GeoKey has only one SHORT item. But I want to demonstrate how you call L_GetGeoKey twice and get the required size in the first call
L_INT GetGeoKeyExample(L_VOID)
{
L_UINT16 *pData = NULL;
L_UINT uCount;
L_UINT uType;
L_INT nSize;
nSize = L_GetGeoKey(1024, &uType, &uCount, NULL);
if(nSize <= 0)
{
MessageBox(NULL, TEXT("The GeoKey was not set, or an error occurred!"), TEXT("FAILURE"), MB_OK);
return nSize;
}
else
{
// allocate an array large enough to store the GeoKey data
pData = (L_UINT16 *)malloc(nSize);
if(pData != NULL)
{
nSize = L_GetGeoKey(1024, &uType, &uCount, pData);
if(nSize <= 0)
MessageBox(NULL,TEXT("Error getting the GeoKey!"), TEXT("FAILURE"), MB_OK);
else
{
// do whatever you want with the GeoKey data
}
free(pData); //// free the pData buffer
}
}
return SUCCESS;
}
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