[Gdal-dev] Pb with CreateCopy from a BMP to MEM

[Stephane Routelous]

Hi Mailing List,

I found a problem (?) in GDAL 1.2.6
I'm create a copy of an image in memory (I tested BMP -> MEM)
The problem is that if I don't specify FlushCache to a band, the
ReadBlock return a empty (zero-ed) buffer
To reproduce, run the following code with commenting out the
"poBand->FlushCache();" line

Perhaps it is a mistake at my side ?

Thanks,

Stephane Routelous
http://www.exotk.org


int main(int argc, char* argv[])
{
	GDALAllRegister();
	GDALDataset* realDataSet = (GDALDataset *) GDALOpen(
"T:\\airport_fence.bmp", GA_ReadOnly );
	if ( realDataSet)
	{
		GDALDriver *memDriver =
GetGDALDriverManager()->GetDriverByName("MEM");
		GDALDataset* memDataSet =
memDriver->CreateCopy("MEM:::",realDataSet,FALSE,NULL,NULL,NULL);
		GDALClose(realDataSet);
		if ( memDataSet )
		{
			int sx = memDataSet->GetRasterXSize();
			int sy = memDataSet->GetRasterYSize();

			GDALRasterBand  *poBand =
memDataSet->GetRasterBand( 1 );

	
///////////////////////////////////////////////////////
			//	Comment the following line out
			//
			//poBand->FlushCache();
			//
	
///////////////////////////////////////////////////////

			unsigned char* buffer = (unsigned
char*)malloc(sx*sizeof(unsigned char));
			poBand->RasterIO( GF_Read, 0, 0, sx, 1, 
                          buffer, sx, 1, GDT_Byte, 
                          0, 0 );

			for ( unsigned int i = 0 ; i < sx ; i++ )
			{
				cout << (int) buffer[i] << " " ;
			}

			cout << endl << endl << endl ;
			poBand->ReadBlock(0,0,buffer);
			for (  i = 0 ; i < sx ; i++ )
			{
				cout << (int) buffer[i] << " " ;
			}
		}
	}

	return 0;
}

Output with poBand->FlushCache();

33 33 21 37 21 33 29 29 29 29 51 61 18 29 42 33 37 37 42 51 42 29 29 46
29 21 37
 21 42 18 37 37 29 25 25 33 10 33 33 14 29 42 33 37 21 37 21 33 25 33 29
33 37 6
1 33 18 37 37 33 33 42 46 46 33 25 42 42 18 29 33 29 29 25 42 29 25 25
37 10 29
37 21 14 51 33 33 37 25 29 25 29 29 29 29 33 33 61 46 14 33 42 33 37 37
46 51 37
 25 37 46 21 25 37 21 42 18 42 33 29 25 33 18 21 37 29 10 46 33


33 33 21 37 21 33 29 29 29 29 51 61 18 29 42 33 37 37 42 51 42 29 29 46
29 21 37
 21 42 18 37 37 29 25 25 33 10 33 33 14 29 42 33 37 21 37 21 33 25 33 29
33 37 6
1 33 18 37 37 33 33 42 46 46 33 25 42 42 18 29 33 29 29 25 42 29 25 25
37 10 29
37 21 14 51 33 33 37 25 29 25 29 29 29 29 33 33 61 46 14 33 42 33 37 37
46 51 37
 25 37 46 21 25 37 21 42 18 42 33 29 25 33 18 21 37 29 10 46 33 


Output without poBand->FlushCache();
33 33 21 37 21 33 29 29 29 29 51 61 18 29 42 33 37 37 42 51 42 29 29 46
29 21 37
 21 42 18 37 37 29 25 25 33 10 33 33 14 29 42 33 37 21 37 21 33 25 33 29
33 37 6
1 33 18 37 37 33 33 42 46 46 33 25 42 42 18 29 33 29 29 25 42 29 25 25
37 10 29
37 21 14 51 33 33 37 25 29 25 29 29 29 29 33 33 61 46 14 33 42 33 37 37
46 51 37
 25 37 46 21 25 37 21 42 18 42 33 29 25 33 18 21 37 29 10 46 33


0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0
0 0 0 0 0 0 0 0 Press any key to continue