rasql - PIXELTYPE=SIGNEDBYTE needs to be casted in encode()

[Bang Pham Huu]

Band 1 Block=128x128 Type=Byte, ColorInterp=Gray
  Min=0.000 Max=56.000
  Minimum=0.000, Maximum=56.000, Mean=0.991, StdDev=4.880
  NoData Value=-128
  Metadata:
    STATISTICS_MAXIMUM=56
    STATISTICS_MEAN=0.99090909090909
    STATISTICS_MINIMUM=0
    STATISTICS_SKIPFACTORX=1
    STATISTICS_SKIPFACTORY=1
    STATISTICS_STDDEV=4.879947749434
  Image Structure Metadata:
    PIXELTYPE=SIGNEDBYTE

will have error for query:

SELECT encode(c[0,0:43,0:55], "image/tiff") FROM
dipteron_infestation_Brazil AS c

with error:

evaluating query with new engine... Unable to convert rasdaman type  to
GDAL type.
Exception: Format conversion failed

It works if this collection is casted, e.g:

SELECT encode((short) c[0,0:43,0:55], "tiff") FROM
dipteron_infestation_Brazil AS c