Change of behavior ?? GDALRasterBand:IReadBlock vs RasterIO ?

[asmita]

Recently seen that GDALRasterBand read for the Mosaics is affected because the read always trying to default to IReadBlock and we never implemented IReadBlock because of less generic type support I guess:

our implementation :
class XRasterBand : public GDALRasterBand
{
 
 public:
  XRasterBand(GDALDataset          *dataset,
                 int                   gdalBandNum,
                 const xyzSize<uint32> &rastersize,
                 const xyzSize<uint32> &blocksize,
                 GDALDataType          gdalDatatype,
                 GDALColorInterp       colorInterp_,
                 const xyzTransferGuard<GDALColorTable> &ctbl_,
                 bool                  haveNoData_,
                 double                noDataValue_);
  virtual CPLErr IRasterIO( GDALRWFlag eRWFlag,
                            int nXOff, int nYOff, int nXSize, int nYSize,
                            void *pData, int nBufXSize, int nBufYSize,
                            GDALDataType eBufType,
                            int nPixelSpace, int nLineSpace,
                            GDALRasterIOExtraArg* sExtraArg);

  virtual CPLErr IReadBlock(int nXBlockOff, int nYBlockOff, void *pabyData){
   CPLError(CE_Failure, CPLE_AppDefined,
             "Internal Error: doesn't support block reading");
    return CE_Failure;
  }

Since we recently upgraded to GDAL 2.1.2 from GDAL 1.1 all the Raster reads are defaulting to IReadBlock for warping /mosaics.

I referred to Migration Guide, but it does not mention of such a change( even the RasterIO RFC is unrelated) - ref :https://svn.osgeo.org/gdal/branches/2.0/gdal/MIGRATION_GUIDE.TXT

My Question is :
1. has anyone seen this issue ?
2. what has changed that may not be documented ?
3. is there a need to implement IReadBlock 2.0 onwards ?

[Even Rouault-2]

On lundi 30 janvier 2017 15:33:28 CET asmita wrote:

> Recently seen that GDALRasterBand read for the Mosaics is affected because

> the read always trying to default to IReadBlock and we never implemented

> IReadBlock because of less generic type support I guess:

>

 

IReadBlock() must definitely be implemented. If you've implemented IRasterIO(), you can easily redirect IReadBlock() to IRasterIO(). For example like done in

https://github.com/OSGeo/gdal/blob/trunk/gdal/frmts/ecw/ecwdataset.cpp#L911

 

>

> Since we recently upgraded to GDAL 2.1.2 from GDAL 1.1 all the Raster reads

> are defaulting to IReadBlock for warping /mosaics.

>

> I referred to Migration Guide, but it does not mention of such a change(

> even the RasterIO RFC is unrelated) - ref

>

> :https://svn.osgeo.org/gdal/branches/2.0/gdal/MIGRATION_GUIDE.TXT

 

> 2. what has changed that may not be documented ?

 

Probably something that did band per band access and was modified to do block per block access. An implementation detail.

 

> 3. is there a need to implement IReadBlock 2.0 onwards ?

 

It has been a requirement since GDAL 1.0. You were just lucky to not have triggered code paths that needed it before.

 

Even

 

 

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[asmita]

I implemented the IReadBlock, still same issue with the WarpOperation  ( that is the code path I am hitting essentially). The issue I see now is the warp does miss some band info or something happens that the entire mosaic is black instead of the imagery. Note that these are non pallette imageries :

implementation:

CPLErr XYZRasterBand::IReadBlock(int nBlockXOff, int nBlockYOff, void *pImage) {


    int nXOff = nBlockXOff * nBlockXSize,
        nYOff = nBlockYOff * nBlockYSize,
        nXSize = nBlockXSize,
        nYSize = nBlockYSize;

    if( nXOff + nXSize > nRasterXSize )
        nXSize = nRasterXSize - nXOff;
    if( nYOff + nYSize > nRasterYSize )
        nYSize = nRasterYSize - nYOff;

    int nPixelSpace = GDALGetDataTypeSize(eDataType) / 8;
    int nLineSpace = nPixelSpace * nBlockXSize;

    GDALRasterIOExtraArg sExtraArg;
    INIT_RASTERIO_EXTRA_ARG(sExtraArg);
   
    return IRasterIO(GF_Read,
                    nXOff, nYOff, nXSize, nYSize,
                    pImage, nXSize, nYSize,
                    eDataType, nPixelSpace, nLineSpace, &sExtraArg);
   
}

WarpOperation : region to buffer call:

void
xyzGDALWarpingReader::FetchPixels(const xyzExtents<uint32> &srcExtents)
{
  warpOperation.WarpRegionToBuffer(srcExtents.beginX(),
                                       srcExtents.beginY(),
                                       srcExtents.width(),
                                       srcExtents.height(),
                                       &rawReadBuf[0],
                                       gdalDatatype
                               );
  }
}

srcExtents acts as a destination buffer for whatever reason in the codebase, and it used to work for GDAL 1.1