[Gdal-dev] BuildOverviews()

[Peng Gao]

Martin,

Thanks for your help. It worked great. The overviews I created are tiled
with block 
size 128x128.

I was using GDALRasterBand::BuildOverviews() on a band and it always
returned error. When
do I ever need to use this call?

Thanks again,
Gao, Peng

> -----Original Message-----
> From: Chapman, Martin [mailto:MChapman at sanz.com]
> Sent: Thursday, November 18, 2004 9:40 PM
> To: Gao, Peng; gdal-dev at remotesensing.org
> Subject: RE: [Gdal-dev] BuildOverviews()
> 
> 
> Gao,
> 
> I've built overviews successfully before for a tif but I 
> can't remember if it was tiled or stripped.  I think I've 
> done both before though.  See the code snippets below if it's 
> any help:
> 
> Let me know if it works.
> Martin
> 
> // this goes some where in your code...
> GDALAllRegister();
> 
> GDALDataset* m_pDataset = (GDALDataset*) 
> GDALOpen(m_sFileName.c_str(), GA_ReadOnly);
> GDALDefaultOverviews* m_pGDALDefaultOverviews = new 
> GDALDefaultOverviews();
> 
> if( m_pDataset == NULL )
> {
> 	const char* pszError = CPLGetLastErrorMsg();
> 	AfxMessageBox(pszError);
> 	return false;
> }
> //........
> 
> 
> // I use this function to generate the ovr file
> 
> void CImagePortDoc::GenerateOverViewFile()
> {
> 	try
> 	{
> 		if (!m_pDataset)
> 			return;
> 	
> 		string ovr_file;
> 		string ovr_name;
> 		string file = m_sFileName;
> 		string::size_type pos = file.find('.');
> 
> 		if (pos == string::npos)
> 		{
> 			ovr_file = file + ".ovr";
> 			ovr_name = file;
> 		}
> 		else
> 		{
> 			ovr_file.insert(0, file.begin(), &file[pos]);
> 			ovr_name = ovr_file;
> 			ovr_file += ".ovr";
> 		}
> 
> 		CMainFrame* pMainFrame = (CMainFrame*) AfxGetMainWnd();
> 		if (pMainFrame->FileExists(ovr_file))
> 		{
> 			CString sMessage = _T("The file ");
> 			sMessage += ovr_file.c_str();
> 			sMessage += _T(" exists.\nDo you want 
> to overwrite it?");
> 			if (AfxMessageBox(sMessage, 
> MB_YESNO|MB_ICONQUESTION) == IDNO)
> 				return;
> 
> 			DeleteFile(ovr_file.c_str());
> 		}
> 		else
> 		{
> 			if (AfxMessageBox("Build the 
> overviews?", MB_YESNO|MB_ICONQUESTION) == IDNO)
> 				return;
> 		}
> 
> 		BeginWaitCursor();
> 
> 		if (!m_pGDALDefaultOverviews->IsInitialized())
> 			
> m_pGDALDefaultOverviews->Initialize(m_pDataset, ovr_file.c_str());
> 
> 		int nOverviewCount = 
> m_pGDALDefaultOverviews->GetOverviewCount(1);
> 
> 		int* pOverviewList = NULL;
> 		nOverviewCount = 12;
> 		pOverviewList = new int[nOverviewCount];
> 		int nNumberOfBands = m_vBandList.size();
> 		
> 		pOverviewList[0] = 2;
> 		pOverviewList[1] = 4;
> 		pOverviewList[2] = 8;
> 		pOverviewList[3] = 16;
> 		pOverviewList[4] = 32;
> 		pOverviewList[5] = 64;
> 		pOverviewList[6] = 128;
> 		pOverviewList[7] = 256;
> 		pOverviewList[8] = 512;
> 		pOverviewList[9] = 1024;
> 		pOverviewList[10] = 2048;
> 		pOverviewList[11] = 4096;
> 
> 		int* pBandList = new int[nNumberOfBands];
> 		for (int n = 0; n < nNumberOfBands; n++)
> 			pBandList[n] = n + 1;
> 
> 		CPLErr err = 
> m_pGDALDefaultOverviews->BuildOverviews(ovr_name.c_str(), 
> "NEAREST", nOverviewCount, pOverviewList, nNumberOfBands, 
> pBandList, GDALDummyProgress, NULL);
> 
> 		if (pBandList) delete pBandList;
> 		if (pOverviewList) delete pOverviewList;
> 
> 		if (err != CE_None)
> 			return;
> 
> 		m_vResLevels.clear();
> 		for (int k = 0; k < nOverviewCount; k++)
> 			m_vResLevels.push_back(k);
> 
> 		UpdateAllViews(NULL);
> 
> 		EndWaitCursor();
> 	
> 	}
> 	catch(...)
> 	{
> 		AfxMessageBox("An unspecified error occurred");
> 	}
> }
> 
> 
> 
> -----Original Message-----
> From:	Gao, Peng [mailto:pgao at esri.com]
> Sent:	Thu 11/18/2004 4:40 PM
> To:	gdal-dev at remotesensing.org
> Cc:	
> Subject:	[Gdal-dev] BuildOverviews()
> I tried to build the overviews on a tiff image, and it failed because
> the format does not support building of overviews. What formats are
> currently supporting building the overviews (pyramid)? I understand
> the overviews if built, are stored in a tiff image with a special
> extension .ovr. Are these overview tiffs tiled or scanline based?
> 
> Gao, Peng
> 
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