[AGG] 8bit AGG/PNG not transparent

[jlacroix]

When using AGG output format in 8bit, the TRANSPARENT TRUE option is not working. The background color is simply black (instead of the IMAGECOLOR yellow). I reproduce the same thing by using a predefined color palette with:

FORMATOPTION "PALETTE_FORCE=TRUE" FORMATOPTION "PALETTE=palette.txt"

Here's a sample mapfile to reproduce the problem: MAP

NAME "AGG256" STATUS ON SIZE 256 256 EXTENT 0 0 10 10 IMAGECOLOR 255 255 0 TRANSPARENT TRUE IMAGETYPE "AGG" OUTPUTFORMAT

NAME "AGG" DRIVER AGG/PNG IMAGEMODE RGB FORMATOPTION "QUANTIZE_FORCE=ON" FORMATOPTION "QUANTIZE_DITHER=OFF" FORMATOPTION "QUANTIZE_COLORS=256"

END

LAYER

NAME "line" STATUS DEFAULT TYPE LINE CLASS

NAME "Province" COLOR 255 0 0

END FEATURE

POINTS

2 2 5 5 5 1 9 9

END

END

END

END