[gdal-dev] IReadBlock fails on alpha band, GDAL 2

[Even Rouault]

> 
> Are there any other problems that you anticipate with using this
> configuration? I see RGBA JPEG-in-TIFF quite often...

I'd expect libtiff based software to generally work fine with that (with the 
exception of this bug of course, which is a rather convoluted way of using 
libtiff and the JPEG driver)

I see that support in libtiff to generate such images is relatively "recent" (4 
years ago) : https://trac.osgeo.org/gdal/ticket/4732

> 
> > Fixed per https://trac.osgeo.org/gdal/ticket/6493
> > Use of implicit overviews can be disabled by defining the config option
> > GTIFF_IMPLICIT_JPEG_OVR=NO
> 
> I can confirm that setting GTIFF_IMPLICIT_JPEG_OVR works and this will
> suffice as a workaround until the next GDAL release. Thanks, Even!

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