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[英]How to obtain latitude and longitude from geotiff image using Gdal C++
[英]How to create dataset from geotiff located in RAM by GDAL
用於打開文件的Gdal函數使用文件名讀取數據,如下所示:
GDALOpen (const char *pszFilename, GDALAccess eAccess)
但我的文件位於內存中。 我使用下一個代碼創建指向文件的指針:
FILE *stream;
stream = fmemopen(buf, lengthOfArray, "r");
是否可以通過某種方式通過文件指針創建GDALDataset?
有技巧和竅門嗎?
GDAL可以選擇從緩沖區創建內存文件。 看到:
http://gdal.org/cpl__vsi_8h.html#a86b6b1c37bb19d954ee3c4a7e910120c
我沒有C ++的經驗,但是在Python中看起來像:
with open('myfile.tif', mode='rb') as f:
gdal.FileFromMemBuffer('/vsimem/some_memfile', f.read())
然后,您可以像打開普通文件一樣打開該虛擬位置:
ds = gdal.Open('/vsimem/some_memfile')
處理完文件后,請確保取消鏈接,否則它會一直存在。
ds = None
gdal.Unlink('/vsimem/some_memfile')
這是在Linux上使用jni處理Java字節數組中的geotiff文件的C ++完整示例:
#include <jni.h>
#include "gdal_priv.h"
#include "cpl_string.h"
#include "cpl_conv.h"
#include "gdalwarper.h"
#include "cpl_vsi.h"
JNIEXPORT void JNICALL Java_com_box_processing_GEOTransform_run(JNIEnv *env, jobject obj, jbyteArray array) {
GDALAllRegister();
jboolean isCopy;
jbyte* buf = env->GetByteArrayElements(array, &isCopy);
jsize lengthOfArray = env->GetArrayLength(array);
const char *pszFormat = "GTiff";
GDALDriver *poDriver;
poDriver = GetGDALDriverManager()->GetDriverByName(pszFormat);
VSILFILE* fpMem = VSIFileFromMemBuffer ("/vsimem/temp.tif", (GByte*) buf, (vsi_l_offset) lengthOfArray, FALSE );
VSIFCloseL(fpMem);
GDALDataset *poSrcDS = (GDALDataset *) GDALOpen( "/vsimem/temp.tif", GA_ReadOnly );
GDALDataset *poDstDS;
const char *pszSrcWKT = NULL;
pszSrcWKT=GDALGetProjectionRef(poSrcDS);
double error_threshold = 0.125;
GDALResampleAlg resampling = GRA_Cubic;
char* pszDstWKT = NULL;
GDALDataset * tmpDS = (GDALDataset*)(GDALDataset*)GDALAutoCreateWarpedVRT(poSrcDS, pszSrcWKT, pszDstWKT, resampling, error_threshold, NULL);
poDstDS = poDriver->CreateCopy( "/some/folder/example1.tif", (GDALDataset*)tmpDS, FALSE, NULL, NULL, NULL );
GDALClose( (GDALDatasetH) poDstDS );
GDALClose( (GDALDatasetH) poSrcDS );
VSIUnlink( "/vsimem/temp.tif" );
}
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