[gdal-dev] Issue with ReadBlock

[trewdbal]

Hi Folks,

I'm trying to read an image using ReadBlock, but the array is not filled
with raster values.
It works with RasterIO.

The code below is copied from the GDAL doc ( page
<http://www.gdal.org/classGDALRasterBand.html#ad80cecc562fd48f5783677de625360ac> 
), I just change the type of the pabyData array (I need float32).
I tested with several raster formats, without result.

Another point, maybe linked with the previous, in the doc at the line :
GByte *pabyData = (GByte *) CPLMalloc(nXBlockSize * nYBlockSize);
I'm confused not reading 
GByte *pabyData = (GByte *) CPLMalloc(nXBlockSize * nYBlockSize *
sizeof(GByte));

Thanks for any help.
Trewdbal

int main()
{
	std::cout.precision(12);

	GDALAllRegister();
	const char* PANFile = "/home/ficus/Code/Covariance/rasters/pan2048.tif";

	GDALDataset  *poDataset;
	poDataset = (GDALDataset *) GDALOpen( PANFile, GA_ReadOnly );

	GDALRasterBand  *poBand;
	int nXBlockSize, nYBlockSize;

	poBand = poDataset->GetRasterBand( 1 );
	poBand->GetBlockSize( &nXBlockSize, &nYBlockSize );

	unsigned int SIZEX = poBand->GetXSize();
	unsigned int SIZEY = poBand->GetYSize();

	int nXBlocks = (SIZEX + nXBlockSize - 1) / nXBlockSize;
	int nYBlocks = (SIZEY + nYBlockSize - 1) / nYBlockSize;

	std::cout << " NBlocks = " << nXBlocks << " " << nYBlocks << std::endl;
	std::cout << " Block Size = " << nXBlockSize << " " << nYBlockSize <<
std::endl;

	float* pabyData = (float*)malloc(nXBlockSize * nYBlockSize *
sizeof(float));

	int nXValid = 0;
	int nYValid = 0;
	
	for( int iYBlock = 0; iYBlock < nYBlocks; iYBlock++ )
	{
		for( int iXBlock = 0; iXBlock < nXBlocks; iXBlock++ )
		{
		poBand->ReadBlock( iXBlock, iYBlock, pabyData );

			std::cout << "test " << pabyData[25] << std::endl; // Where we see that
the array is full of 0 values...

			// Compute the portion of the block that is valid
			// for partial edge blocks.
			if( (iXBlock+1) * nXBlockSize > poBand->GetXSize() )
				nXValid = poBand->GetXSize() - iXBlock * nXBlockSize;
			else
				nXValid = nXBlockSize;

			if( (iYBlock+1) * nYBlockSize > poBand->GetYSize() )
				nYValid = poBand->GetYSize() - iYBlock * nYBlockSize;
			else
				nYValid = nYBlockSize;
		}
	}

	free(pabyData);

	GDALClose( poDataset );

	GDALDestroyDriverManager();
	return 0;
}




--
View this message in context: http://osgeo-org.1560.x6.nabble.com/Issue-with-ReadBlock-tp5246218.html
Sent from the GDAL - Dev mailing list archive at Nabble.com.