DRAW_ALPHA

DRAW_ALPHA_NONE No alpha.
DRAW_ALPHA_INVERTED Generates inverted alpha.
DRAW_ALPHA_NORMAL Generates alpha channel from the image’s alpha channel. If no alpha channel exists, the alpha value is set to 100%.
DRAW_ALPHA_FROM_IMAGE Generates the alpha channel from the RGB image information.
DRAW_ALPHA_NORMAL_FROM_IMAGE Generates the alpha channel from the image’s alpha channel. If no alpha channel exists, the alpha value is generated from the RGB image.