[gdal-dev] OpenJpegDataset IReadBlock question

[Robert Zermeno]

Ladies and Gents,

I have yet to properly configure GDAL to compile with a repository OpenJpeg V2, but I wanted to see how GDAL uses openjpeg tile request.  I created my own project and modified IReadBlock() to be standalone to view a tile request.

I am using a sample data file provided by openjpeg data folder named p1_04.j2k.  How is the data retrieved from opj_decode_tile_data() is being stored in the buffer?  To access pixel 0, is it just buffer[0] or is there another way?
For some reason, my request for Tile (0,0) of length 128x128 returns an image that looks masked.  The image is mostly black and white with no depth of shading (i.e. missing information).  
This image also uses 12 bits-per-pixel which I do not see where GDAL truncates the image data down to 8 bits-per-pixel.  Does GDAL return the raw 12 bits-per-pixel forcing the user to truncate the data properly for every pixel or is it handled by GDAL (If so, where)?

I hope to figure out why GDAL does not link properly to openjpeg V2 for others use this option again.  I hope someone can provide me the answers to the questions I have asked.

Thanks,

John
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