OFFSITE pixels are not transparent using AGG

[sdlime]

It appears that the AGG renderer doesn't make OFFSITE pixels transparent for RASTER layers. I'm not sure if the problem lies in the AGG code or in the GDAL code. My test is limited to a series of TIFF images (8-bit palleted, 24-bit RGB and 48-bit RGB). The layer def looks like:

LAYER

NAME 'TEST_IMAGE' TYPE RASTER DATA 'test_color.tiff' OPACITY 50 OFFSITE 0 0 255 STATUS DEFAULT

END

With 16-bit channels I include PROCESSING "SCALE=AUTO". I'll upload a couple of samples with and without AGG and the source image. GDAL seems to be processing the OFFSITE colors correctly as they turn from blue to black but the offsite pixels aren't transparent with AGG.

Steve

[tbonfort]

duplicates #2540