This function can be used to retrieve the current destination extended blend mode alpha factor. The value returned will be one of the following constants ("s" denotes a value taken from the source while a "d" denotes a value from the destination) with only the "A" component being used when drawing:
Constant Blend factor (Red, Green, Blue, Alpha) bm_zero (0, 0, 0, 0) bm_one (1, 1, 1, 1) bm_src_colour (Rs, Gs, Bs, As) bm_inv_src_colour (1-Rs, 1-Gs, 1-Bs, 1-As) bm_src_alpha (As, As, As, As) bm_inv_src_alpha (1-As, 1-As, 1-As, 1-As) bm_dest_alpha (Ad, Ad, Ad, Ad) bm_inv_dest_alpha (1-Ad, 1-Ad, 1-Ad, 1-Ad) bm_dest_colour (Rd, Gd, Bd, Ad) bm_inv_dest_colour (1-Rd, 1-Gd, 1-Bd, 1-Ad) bm_src_alpha_sat (f, f, f, 1) where f = min(As, 1-Ad)
Constant (see above table)
bm = gpu_get_blendmode_srcalpha();
bm = gpu_get_blendmode_destalpha();
gpu_set_blendmode_ext_sepalpha(bm_inv_src_alpha, bm_inv_dest_colour, bm, bm);
The above code creates a local array and gets the current source and destination blending factors for the alpha component. This array is then used to manipulate the RGB component of the blending factors.