This enumeration specifies the Reduction Method the Source should use to reduce the bit depth of the data.

Values:

IG_TW_BR_CUSTHALFTONE	Custom Halftone method.
IG_TW_BR_DIFFUSION	Diffusion method.
IG_TW_BR_HALFTONE	Halftone method.
IG_TW_BR_THRESHOLD	Threshold method.