[gdal-dev] JPIPKAK dataset usage

[Garrett Potts]

Hello All:

I am trying to use the jpipkak data set driver for testing JPIP calls to a JPIP server and I think I am having troubles trying to figure out the proper call to GDALRasterIo for the proper load of the requested region of interest.  I have tried 2 ways,  using the block IO and also trying to use the GDALRasterIO call.  I am simply trying to use an application to sequence over the blocks at a given R-Level and write to a file.  Seems what I think the RLevel rect should be in the call is not what the JPIP driver expects:

Here are a pseudo step of what I am doing in our own image loader and all the open fluff has been removed and the dataset has been verified to get the image dimensions, pixel type, … etc properly from the JPIP stream:

1) grab resolution band:
 
if res level is 0 or full res then init:

 aBand = GDALGetRasterBand( theDataset, aGdalBandIndex );

if overviewIndex is > 0

aBand = GDALGetOverview( aBand, overviewIndex );

2) grab blocksize:

      int xSize=0, ySize=0;
      GDALGetBlockSize(aBand,
                       &xSize,
                       &ySize);


3) now iterate over resolution level by the block sizes and grab the data.  I have tried this with GDALReadBlock and GDALRasterIO.


The driver gets data but it is in the wrong resolution which means I am not calling these with the proper request.  I have traced the code but something doesn't quite make sense to me.  It appears the R-Level is computed based on the input request versus the output width height buffer ratio.  I think everything would get cleared up if I could see some example calls using above methods in when using the JPIPKAK dataset driver.


Thank you in advance for any help

Take care

Garrett